Scale in Transformers is, not to put too fine a point on it, screwed.
Virtually no era, franchise, fiction, toyline or other incarnation of Transformers has presented scale in a logical or believable fashion. (The only exceptions are the 1:24 toys for Alternators and Kiss Players, but they have their own problems.) Most fans agree that one must either ignore it or accept it, lest they be tempted to explain these problems and in the process fanwank themselves into oblivion.
However, the scale problems of Transformers still merit description.
Scale within toylines
Toys out of scale with others in the same line
The early Generation One toyline, especially the pre-movie lines, were repackaged and redecoed toys from several different Japanese toylines. The crucial point is that the toylines were initially unrelated. The characters should be in scale to each other as they all have real-world altmodes that (should) pass for real vehicles. However, since Diaclone toys were not part of the same line as Microman toys, scale issues arose. Diaclone figures such as Optimus Prime, Prowl and Hound are more-or-less in correct scale to each other (though problems already arise with Sunstreaker and Sideswipe, whose alternate modes are based on the same car yet are not quite the same size), but many of the Mini Vehicles from the New Microman line are clearly far too small by comparison. Even aside from their deformed penny-racer proportions, a Volkswagen Beetle Microman toy is disproportionately tiny when compared to a Porsche 935 Diaclone toy. The disparity becomes even more obvious with Minibots such as Warpath (a tank) and Seaspray (a hovercraft), who should be many times their actual size.
Another glaring scale problem comes in the form of the Seekers, who turn into F-15 Eagles which, in real life, are 19.4 m (63.8 feet) long. Correctly scaled, this would make their robot modes colossal compared to most Autobots. Similarly, the Constructicons, despite also coming from the Diaclone line, are too small. Far worse is the other Diaclone combiner team, the Trainbots, who have train engine altmodes, yet their toys are among the smallest of the Diaclone releases.
Mini-Cons are always out of scale, either with their vehicle or with each other. Mini-Cons such as Buzzsaw (a bucket wheel excavator) being waaaaay out compared to others like Swindle (a Formula 1) who's toys are the same size. Almost all 'cons are out of scale with their vehicle forms. For example Buzzsaw (again) who as you already know is a huge machine in alt mode is human sized in robot mode. Yep just about every 'con has this problem, whether they turn into ground vehicles or aerial vehicles they are guaranteed to be out of whack with themselves. This, however, is jusitifed in fiction featuring the characters, where it is established that Mini-Cons are supposed to be very tiny vehicles that are the same size, regardless of their variance in form.
Toys out of scale within teams
Even toys specifically designed to interact with each other suffer from this problem. The Combaticons are wildly out of scale to each other — Blast Off's space shuttle mode should dwarf Swindle, with the others somewhere in between. Instead, they're about the same size. Among the Constructicons, Long Haul is designed to look like a gigantic "earth-mover" mining truck. He should be able to carry all his teammates in his bed, with some crowding. Similarly, Silverbolt (a Concorde jet) is dramatically undersized compared to his fighter-jet Aerialbot teammates. These scale problems are necessary to avoid misproportioned gestalt forms.
Same altmode, different sizes
Other scale problems come from characters who transform into the same (or similar) altmodes but whose toys are different sizes. For example Air Raid transforms into an F-15 Eagle, but his toy is half the size of Starscream's. The same can be said for the Lamborghini Countach Breakdown, who should be the same size as Sunstreaker and Sideswipe, not significantly smaller. These discrepancies are also seen in the other Scramble City combiners with Earth altmodes, whose toys are all smaller than similar earlier toys.
Multiple scales of same character
|Too much rant; missing: BM Supreme/Night Slash etc. Cheetor; RID Spychangers (Prime, Magnus, X-Brawn, Scourge); Cybertron and Movie Legends; Energon/Superlink Megatron/Galvatron and Prime; Cybertron Supreme and Voyager Starscream (albeit explained in-story); Animated Activators; etc. pp.|
Although this was never really a problem in G1 (later retro-iterations of G1 Prime e.g. Masterpiece don't count), later franchises sometimes released multiple versions of the same character in different size classes within the same product line, usually limited to the leader characters. Multiple versions of Optimus Primal and Megatron in Beast Wars weren't exactly an example of this, as they represented different bodies (Beast Machines contained an arguable example with Primal, but this was obfuscated by poor show-accuracy and product delayed into the RID line).
The first real example was the Armada line's super-con and super-base versions of Optimus Prime featuring the same design at different size-classes, an issue repeated with Megatron in Energon. This pattern became more prevalant with the Movie toyline which offered both Voyager and Leader-class iterations of Prime and Megatron. The fact that Blackout came with a small Scorponok, and about at the same time, a deluxe class Scorponok was released, adding further confusion, especially considering the two can clip together 'while' blackout carries the smaller version, in effect transporting 'both' at the same time. The fact that Prime and Megs are apparently the same size in the toyline, but in the movie, Prime is smaller, Bumblebee is the same size as Prime. Starscream is a bit smaller then Megs, but the same size as Bumblebee in the movie?? WhAt?
This confusion of scale has gotten even worse in the Transformers Animated (toyline), with Activator, Deluxe, Voyager, Leader and even Supreme-class versions of Optimus and Megatron, and many other characters in multiple sizes. The Voyager class isn't that much bigger than the Deluxe class, resulting in quite a few scale problems such as the lankier characters like Deluxe Blackaracnia being almost as tall as stubbier but technically much larger characters like Voyager Bulkhead, and the very lanky Deluxe Lockdown taller than nearly any Animated Voyager class toys.
This was intended to make popular characters like Optimus and Megatron available at lower prices so that children with less money would not miss out, while also forcing completist collectors to buy multiple versions of each character. The result, however, is that it creates further confusion about scale within the toyline, as the contradictory sizes of these toys leave it up to the fans to determine which is the "correct" version, either using apparent show-accuracy or other criteria.
Toys out of scale with themselves
Triple-Changers create a whole new set of problems. Octane transforms from a 20 m (60') tanker truck into a 65 m (200') jumbo jet. Broadside transforms from an Earth jet into an entire aircraft carrier.
Even a two-mode toy can have this problem. Twentieth Anniversary Optimus Prime has wheels which are pretty tiny for a Freightliner truck, while his rear hitch section is too thick. These out-of-proportion vehicle parts were necessary to give his robot mode show-accurate proportions.
Toys with roleplay altmodes
The characters with roleplay altmodes such as Generation One Megatron, Soundwave, Perceptor, or Armada Laserbeak are scaled to be human-scale (well, kid-scale). Since the size changing seen in the fiction is not possible for real toys (at least, that's what Takara wants us to think), this human-scaling makes in some cases for inordinately large robot modes. E.g., Blaster's toy, in robot mode, is taller than most other Transformers. For characters such as Megatron, it enables his robot mode to be in scale with other characters' robot modes while the alternate mode is in scale with a normal human being - but that just complicates things even more.
The opposite problem is seen with Masterpiece Megatron, whose robot mode is in scale with Masterpiece Optimus Prime. The result is that, while he may transform into a very accurately-proportioned handgun, it's unmistakably much larger than the real thing (Not that this has stopped him being widely banned as a "realistic firearm replica"...).
Most post-movie Generation One characters (for that matter, most post-Generation One lines) are difficult to accurately scale, as they generally transform into futuristic or Cybertonian vehicles whose size we don't really know. (Or, indeed, they don't transform into vehicles at all.) The scale of characters such as Hot Rod or Leobreaker is fairly arbitrary and can only be estimated by their relative size to other characters in the fiction (although most fiction is highly inconsistent in this regard, see below). Nevertheless, if one assumes that most vehicle altmodes are intended for human-sized passengers, comparing toys such as Chromedome and Lightspeed suggests the combiner scale problem continues.
It goes without saying that the city-bot and planetbot toys (such as Fortress Maximus and Unicron) are not remotely to scale with normal Transformer toys. While they are indeed large toys, they're only two to five times bigger than typical Transformer toys, and thus transform into "cities" and "planets" about the (relative) size of a bungalow. The scale problems extend to the details. Some of the citybot toys have visible windows, which are too large for a city, suggesting instead a medium-sized building.
However, it's hard to begrudge Hasbro not offering us a Primus toy the size of an asteroid. Where would we keep it?
There has only been one notable exception to all of this scale weirdness in the toys: the Alternators toyline, where every toy is a 1:24-scale representation of a real car, and thus they are in perfect scale with each other. Unfortunately, for practical reasons this limits the choice of altmodes. A Blast Off (space shuttle) toy in scale with the Alternators toys would be 1.6 m (5.1') long, while a Broadside (Nimitz class aircraft carrier) toy at that scale would be over 12 m (40'). (Hasbro actually displayed mock-ups for an unproduced line of "military" Transformers in scale with the Alternators during the BotCon 2007 Hasbro Tour; two of them recycled parts of Armada Unicron, and were thus Supreme-sized, which made said potential toyline not particularly commercially viable for Hasbro.)
Scale within fictions
Scale issues abound within the fiction, especially the Generation One cartoon. Some can be attributed to animation errors, such as layering problems,123 but some "errors" were deliberate choices, for a variety of reasons.
Fictional scale vs. toy scale
Transformers fiction often depicts characters to the same relative scale as the toys, which duplicates the intra-toyline problems described above. The cartoon, for example, shows Prime, Megatron and Soundwave as about the same height, Seekers and Autobot cars as slightly shorter (though not as much as the toys are), and Minibots as smaller yet. This scale was carried over to their vehicle forms, resulting in differently-sized cars that, based on real world measurements, should be virtually the same size.
For another example, the Marvel Comics portrayed the Pretenders as literal interpretations of their toys: 60-foot humans with full scale Transformers inside. The "disguise" aspect of this was later explained by having Landmine and Cloudburst encounter gigantic alien organics on other worlds, who regarded 60-foot humans as entirely normal.
Transformers fiction commonly shrinks or inflates characters, relative to their toy sizes. "Giant" characters such as Omega Supreme are, even aside from any size changing for transport purposes, clearly not in the same scale in toy form as they are depicted on screen. Cassette characters such as Rumble's toys are roughly the same height as most Minibots, while in the show they are usually portrayed as human-sized.
Rodimus Prime and Ultra Magnus are usually shown to be of a fairly similar height (although Magnus is much bulkier), whereas there is a considerable difference between the size of their toys. By the same token, Rodimus is always depicted as being an equal stature to his opposing leader Galvatron, whereas the toy Galvatron is instead the same size as Magnus. Optimus Prime is also usually shown as only a head or so shorter than Magnus (if that), which gets very strange when you realise that a redeco of Prime's toy forms but a small part of Magnus' robot mode.
Cybertron Metroplex and the other citizens of Gigantion are depicted as gargantuan in animation, whereas the toys are merely among the normal boxed size-classes. Within the animation, this causes problems with their Mini-Con partners, who are depicted as human-sized in robot mode by themselves, but when shown directly interacting with their larger partners, are scaled up right along with their partner... resulting in some temporarily gigantic Mini-Cons!
The cast of Beast Wars were size-tweaked quite a bit, relative to the toyline. The most noticeable problem is Optimus Primal, who has an Ultra toy (the "level four" size, almost twice the size of the "level three" Mega next-largest Maximal toys), but is shorter than both Dinobot and Rhinox (both of whom are "level two" Deluxe sized toys). Further, Cheetor and Tigatron's toys use the same (Deluxe) mold, but Tigatron is a head taller in the show (both because tigers are larger than cheetahs, and because Cheetor is "a kid"). New and altered characters in later seasons were generally more consistent in size (and appearance) with the toys.
The Beast Machines' toyline was far worse in size discrepancies with the cartoon. Of the Maximals featured in the show, the tallest character, Silverbolt, is the shortest toy, while the diminutive Nightscream is a massive Ultra-class toy. And, sadly, the most show-accurate toy, Air Attack Optimus Primal, is a ginormous Supreme figure, towering over the other toys. (Weirdly, the King Kong-like size of this toy became canon in one specific micro-continuity.)
Even if a size was decided on, it often didn't remain consistent. The height of the cartoon's Skyfire, just to name one, frequently varied between episodes.
The Generation One Marvel comic is notorious for changing the relative sizes of various characters. A single Transformer's size is rarely consistent between artists. For example, Rumble and Frenzy vary in height relative to Soundwave. A panel in the Time Wars shows Goldbug, Ironhide, Scattershot, and Swoop all the same height. Omega Supreme, titanic in his original appearance, shrunk steadily in subsequent issues until he was not much taller than the average Transformer. Fortress Maximus suffered a similar problem, shrinking in size even though he was explicitly rebuilt to be twice as tall as the average Transformer.
Between the Great War and the Beast Era, the majority of the Cybertronian race considerably downgraded in size. When entering the Ark, the Beast Warriors are quite small compared to the dormant Generation One characters, especially Optimus Prime -- but just how much bigger varies quite a bit from scene to scene and episode to episode. When interacting with the Autobot technology of the Ark and the Autobot shuttle, the Maximals are often dealing with equipment grossly oversized for them (standing on the chairs to reach the controls, turning knobs the size of their heads); yet the Ark also seems to feature some human-sized control panels, such as the computer in Master Blaster. Without any height booster, Blackarachnia can interface well with these controls.
On the other hand, Robot Masters depicted Generation One and Beast Wars characters like Optimus Prime and Optimus Primal as being exactly the same size. Lovely. It's possible that passage through the Blasty Zone may somehow account for this discrepancy.
Explicit size changes
Numerous characters are explicitly shown to shrink or expand at various times.
Human-scaled alternate modes
Soundwave becomes a human-scaled tape-deck, Blaster becomes a human-scaled radio and Megatron shrinks into a Transformer-scaled handgun. The cartoons and comics typically show this without explanation, leaving the reader to attribute it to advanced alien technology.
Some versions of the Pretenders are shown to explicitly shrink when hiding in their human-sized outer shells. In the U.S. toy commercials, Grimlock, Bumblebee, and Jazz in their new Pretender forms were small enough to fit in Powermaster Optimus Prime's hand. So, at least in that micro-continuity, they were human-sized. Super-God Masterforce featured Pretenders who did not have outer shells but rather an ill-defined holistic transformation which explicitly involved size changing. A vaguely similar explanation appeared in Dreamwave's More Than Meets The Eye encyclopedia.
Implicit size changes
Characters often change size when transforming in a less explicit fashion. These changes in scale are usually attributed to size changing by that portion of the fanbase who like to find explanations for things. The other explanation is that the artists hoped the audience wouldn't notice.
In the orginal cartoon, Transformers that act as transport for other Transformers, such as Astrotrain, Skyfire, and Cosmos, will often dramatically change size relative to their compatriots between one shot and the next. For example, Cosmos is much shorter than Blaster in robot form; yet Blaster easily fits within his spacecraft mode. Likewise, the Constructicons are able to combine into a fully formed Devastator inside the cargo area of Astrotrain's shuttle mode with plenty of room leftover for the rest of the Decepticons, yet Astrotrain is the same size as most other Decepticons in his robot mode.
Sometimes the cartoon would show ordinarily-scaled characters such as Cyclonus, Thrust or Huffer carrying another Transformer in their cockpit, implying either a tiny passenger or a huge vehicle. Even Omega Supreme, who is supposed to be huge, would have to have a greatly expanded scale for his rocket ship component to accommodate passengers as shown on the cartoon.
The Marvel comics commonly sidestepped this issue by not using Transformers as transport characters, or else requiring the passengers to transform into their explicitly smaller forms to be carried. Yet they were not immune to this problem. In one story, the Pretender Cloudburst exited his shell, transformed into jet mode, and then his shell (and Landmine) boarded him as a passenger. The fact that his outer shell was now much smaller than the inner robot was quietly ignored.
Combiner characters are often depicted as far larger than the sum of their parts. Characters such as Devastator and Menasor are frequently shown as Godzilla-sized. Given that their limbs are mere cars and construction vehicles, this is patently absurd. (Superion, by contrast, would be building-sized, given that his torso is a 100-seat jetliner.)
Combiners are also often out-of-scale with other Transformers; a combiner with cars for legs and another car for its torso should be only twice as tall as a one-car Transformer, but they are routinely drawn as five to dozens of times taller than their comrades.
Scale problems and size-changing
Some fans interpret the many otherwise-unexplained scale issues above to all be the result of size changing, but this is debatable. If virtually all characters use mass-shifting (or whatever) to gain or drop a few feet of height for no logical reason, the technology would be pointlessly mundane. There's also no known reason for (e.g.) the Seekers to choose to get shorter when going into battle. A to-scale Starscream in robot mode could kick Bumblebee around like a soccer ball. There's simply no positive evidence that size-changing is so widespread.
Undersized alternate modes
Many Transformers are portrayed in fiction as having alternate modes that are smaller than the real-life objects they are imitating. Sometimes this is deliberate, allowing them to match their toy scale and/or be of a similar size to other characters; in other cases, it is essentially an artistic error.
Toys at the lowest price points usually include "mini" or "micro" in their name. They are usually depicted as smaller than other Transformers in the fiction, even when their alternate modes should have them towering over other characters. This often results in miniscule vehicle forms; Seaspray is a tiny hovercraft, despite being covered with doors and windows.
The Micromasters are explicitly downsized Transformers, roughly the size of a human in the comics, meaning that they should have explicitly tiny vehicle modes... which wouldn't make for very convincing disguises. The Micromasters are about the same height in robot-mode, but they transform into equally-tiny cars, trucks, planes, tanks, and other vehicles that should be vastly different sizes.
Despite this, the Marvel comic featured Roadhandler carrying a human passenger in his vehicle form, as though he were a full-sized car. The Dreamwave miniseries Micromasters suggested that the Micromasters were scaled down to more easily interact with "smaller beings". It does not explain the Micromasters' passenger compartments, which are obviously much too small to accommodate the "smaller beings".
The Mini-Cons of the Unicron Trilogy are another race of small robots who stand approximately the same height as humans and, like the Micromasters before them, are clearly modeled to carry passengers. Really teeny passengers. (Notable exceptions are Grindor (in his original body), Sureshock, and High Wire, who become small one-man conveyances.) In this continuity, there's no sign of mini-passengers. The Mini-Cons scan normal vehicles and then resize them to fit, retaining now-useless passenger compartments. In the Cybertron cartoon, the Recon Mini-Con Team have slightly-larger-than-human robot modes, but their alternate modes are large enough for a single human passenger, implying either a little size-changing, or that their cockpits are kinda cramped.
Likewise, the Beast Era Maximals and Predacons possess roughly human-size bodies; yet when portrayed as vehicles on Cybertron ("Dawn of Future's Past", the Vehicons in Beast Machines), they feature seats and cockpits that, at their size, should be basically useless.
The characters Metroplex, Trypticon, Fortress Maximus and Scorponok have "city" alternate modes. As actual real-life cities can sprawl for many miles, a city-bot that can notionally house a population of humans, let alone transformers, should have a robot-mode that would make Godzilla look like a gecko. Suffice to say, almost no fiction even begins to approximate the logical size of a true "city-bot". In the American and Japanese cartoons, all four were shown as massive robots capable of housing many normal-sized Transformers. However, the grossly-undersized depictions of Unicron (see below) would be closer to the size of a transformed city; in the context of Transformers, "city" is perhaps better read as "apartment" or "fortress".
These city-bots often have "small" robots forming vital components. Scorponok has a "human-sized" being forming his head. Full-Tilt, Six Gun, and Slammer must logically be building-sized in robot-mode to be in-scale with Trypticon and Metroplex, but, again, are not drawn as such.
The Marvel Generation One comic sidestepped this issue by depicting Trypticon, Fortress Maximus and Scorponok as merely "large-standard" characters.
Planets and planetbots
Scale when it comes to planets is so fraught it's painful. The problems of describing citybots as "cities" is a thousand times worse if Unicron is supposed to have a planet alternate mode, and Cybertron is in turn supposed to be of similar size. Though different stories have compared Cybertron/Primus and Unicron to drastically different real planets, the fact remains that they are planets, and yet are shown in such insane scale to characters as to suggest they are the size of a very small moon (or space station).
To start with, Cybertron was shown throughout Generation One with buildings visible from space. Although this was intended to show that the planet was technological in nature, it makes little sense, as the structures would have to be the size of small nations to be visible. If the buildings were in fact supposed to be skyscrapers (or even 2000 A.D. style arcologies) sized for 10 m (30') robots, Cybertron would still be less than 150km (100 miles) across. By comparison, the rather Coruscant-like shots of Cybertron in Beast Machines may be less distinctive or "Cybertronian", but are far more believable.
It states however in the first issue of the Marvel comics Transformers, that Cybertron is a "Jupiter sized world". But, contradicting this statement, in The Transformers episode "The Ultimate Doom, Part 2", it is revealed that Cybertron in this continuity was in fact half the size of Earth's moon. Thus, making it possible that buildings can be seen from space. As well, the size of Cyberton could become roughly the size of a state or county.
Unicron is a more extreme problem. Assuming no size changing occurs during his transformation (and really, what possible reason would he have to become smaller?), in robot mode he would be so massive that any shot featuring a recognizable part of his body, let alone the whole thing, would be on a scale such that no normal Transformer would even be visible. Scenes in the Movie in which he directly interacts with normal Cybertronians are blatantly absurd (though totally phat-looking). Shots such as the Dinobots fleeing his grasping hand, a starship penetrating his eye, impaling Brainstorm on his fingernail (in the comic), or especially him picking up Galvatron between his fingers before swallowing him, break any concept of "planetary" scale. If Unicron as a planet is about the size of Earth (it's as good a size for him to be as any), his hands would be the size of Western Europe. This would make Galvatron (in the image to the right) the size of Ireland.
There is no explanation for any of this. Just go with it. However, since Cybertron is smaller than the moon and it has been shown that Unicron is smaller than Cybertron, it is most likely that Unicron is the size of a county or large city. This explaining that his head is the size of a city (more specifically Trypticon or Metroplex) and his hands being smaller than his head allows easy interaction with large Transformers (such as the Dinobots).
The depiction of Unicron's scale in Armada was (debatably) a slight improvement, in that physical interaction with normal beings was not attempted. He preferred instead to communicate with normal Transformers by possessing one of them. Nevertheless, shots featuring Thrust and Megatron standing on his neck are still farcically out of scale.
Oversized alternate modes
Much less common are instances of a Transformer turning into an overscaled real-world object. Most such instances occur in the Beast Wars era.
Although the Beast Warriors are consistent day-to-day in their relative size to each other, their scale in relation to their real-world animal equivalents is more complex. While the bug characters such as Waspinator and Inferno are obviously scaled-up, most of the characters are subtly not quite the right size.
Cheetor and Tigatron are shown standing next to real members of their species, and they are both the same size as the animals in question. This makes them (and Cheetor in particular, since he's around more) the measuring sticks for the other characters. Therefore, Rattrap is a monstrously huge rat, the size of a medium sized dog such as a Labrador (indeed, the writers stated that Season 1 Rattrap was 5' (1.5 m) tall). Dinobot is considerably larger than a real velociraptor, closer in size to a Utahraptor. Rhinox is about half the size of an adult rhinoceros, and Optimus Primal is a roughly normal (or female) gorilla. However, Megatron is a tiny specimen of T. rex (Perhaps a Nanotyrannus? ).
In their interactions with adult protohumans, the Transformer characters seem between twice and three times their height. Considering our ancestors really were smaller than modern humans, this is not extremely wrong, but it deserves noting.
Variation for characterization
Some scale problems are for the sake of characterization. For example, Optimus Prime is routinely shown as thoroughly gargantuan, several stories in height, and capable of cradling humans in his palm. If he's the size of a real truck, Prime in robot mode should be 8–10 m (25'–30') tall, at best. He's drawn large because he's a leader character.
Conversely, Bumblebee is sometimes shown only a few feet taller than an average human, while in reality he would be 3–5 m (10'–15') tall (the Marvel comic actually states he's 15' tall). He's drawn small because he's a human-friendly character, and a junior member of the Autobots.
With fighter jet alternate modes, the Seekers should be among the largest everyday Transformers and would tower over their Autobot adversaries; instead, the animation depicts characters such as Thundercracker and Wheeljack as about the same height. Though jets are much larger than cars, they're drawn the same height so the battles appear fair. (And also to make it easier to animate; blocking a shot where characters differ radically in height is difficult.)
In a related vein, sometimes Transformers are able to enter human buildings, fitting through their doors and able to run up their staircases without crashing through. A cast that couldn't enter buildings would be grossly inconvenient for telling some stories, so the animators fudge things.
Intentionally strange scale
Sometimes artists draw a character at a different size intentionally. For example, on the cover of the first issue of Marvel Generation One, Optimus Prime is extremely huge, compared to the highway, bridge, and normal cars. (Laserbeak is bigger than usual, too.) This is purely for dramatic effect.
Another notable example is the splash screen for the "World of the TRANSFORMERS" website, which depicts Optimus Primal (in his original gorilla body) as the same size as G1 Optimus Prime and Movie Optimus Prime, directly contradicting the size difference seen in "Optimal Situation" and elsewhere.
Live-action film continuity
The creators of the live-action movie took great pains to avoid out-of-scale issues. (Well, greater than previous franchises.) This is sometimes reflected in the choice of vehicle or the design of their robot mode. E.g., Optimus Prime is an extended-hood cab in order to have more mass with which to make a taller robot mode. Starscream's robot mode is nearly as wide as it is tall, with shorter, digitigrade legs, so the massive jet-former won't end up twice as tall as Optimus. In the case of Blackout, his massive alternate mode simply results in a hulking, towering robot mode.
There are still minor scale issues to be found, though. For example, Optimus Prime can hold both Sam and Mikaela in one hand. Comparing this shot with when he picks up Archibald Witwicky's glasses a few minutes later, it seems the glasses have lenses a foot (30cm) in diameter. This is a visual cheat so the glasses are visible to the audience. There's also debate about whether Frenzy's head could compact itself into a slim mobile phone (however it is possible that with all the empty space in Frenzy he could simply fold up). The movie-franchise toys, meanwhile, are only intermittently consistent (particularly since some of the secondary ones are redecos of toys from previous lines), with the largest contrast among the "primary" toys being between Deluxe Class Arcee, a motorcycle, and Voyager Class Decepticons with helicopters as their alternate modes, such as Blackout and Incinerator. However, many of the wheeled vehicles are close to 1:35 scale, although Deluxe Class Jazz and 1977 Bumblebee are obviously not the same scale. Strange how deluxe Arcee is bigger in vehicle mode than deluxe Wreckage in vehicle mode.
In the film Revenge of the Fallen, the scale issue is more evident. Mudflap and Skids start out as two halves of an ice cream van and yet somehow each of them can reformat themselves as a whole car (must have been one massive van to begin with).
Scale issues in the Prime cartoon afflict almost every member of the cast. All of their humanoid modes are all larger than their altmodes could realistically produce. However, to balance this out, their size differences with their altmodes are only minor — except for some errors.
There are only a few major exceptions to this. First is Arcee, who has an altmode literally the size of her leg, she changes her "mass" size so upon transforming to humanoid mode, yet her tires remain the same size. Also, Airachnid has the alternate mode of a chopper, yet she is closer in size to Arcee in humanoid mode while shorter than Breakdown and Knock Out.
Official Scale GuidesAnimators and comic book artists received official scale guides showing relative and (in some cases) absolute heights. Some of these were published in the character model guide Transformers: The Ark. Though they were sometimes ignored, they still give insight into the official scale of characters in Generation One. However, even here, there are problems. Devastator in the Season One scale guide was approximately 2.5 times the height of Optimus Prime, but by Season Two he was somewhat less than twice Prime's height.
- Estimated "real-life" heights for several Transformers, derived from the size of their alt-modes, archived from alt.toys.transformers on groups.google.com