How big is Bahamut?

[axemtitanium]

I was curious about just how big Bahamut is. Inspired by xkcd, I will use Fermi estimation to calculate a ballpark guess for how large the elder primal is.

Assumptions:

1. Hydaelyn is a roughly Earth-sized planet. Mean radius = 6371 km.
2. Menphina is a roughly Moon-sized natural satellite. Mean radius = 1737 km.
3. Dalamud is roughly as small compared to Menphina as the Moon is to Earth.*
4. Bahamut's wingspan is roughly twice the diameter of Dalamud, according to the End of an Era trailer.
5. Bahamut's height is about 1/3 the length of one wing.

*This is the most difficult assumption because there is no accurate way to estimate the size of Dalamud from a land-based observer. Twin moon systems like Menphina and Dalamud are exceedingly rare in nature so it's challenging to find a good estimate of what counts as "reasonable" or "reasonably possible".

Given these assumptions, let's crunch some numbers.

• 1737 km radius of Moon / 6371 km radius of Earth = 0.2726; the Moon is roughly 1/4 the radius of the Earth
• 1/4 * 1737 km radius of Moon = 434.25 km; Dalamud is just over 400 km in radius
• 400 km radius of Dalamud * 2 (for diameter) * 2 (for double diameter) = 1600 km; Bahamut's wingspan is about 1600 km
• 1600 km wingspan * 1/2 (one wing) * 1/3 = 267 km height

For reference, 1600 km is about the same distance from Berlin to Moscow (alternatively, about half the distance between Washington, DC and Los Angeles). Eorzea has been compared to the size of Europe so I'd guesstimate this to be around the same distance between Limsa Lominsa and Gridania. In other words, Bahamut is really frickin' big. Even with a conservative Fermi estimate, Bahamut's wingspan would still be on the order of 1000 km (3 orders of magnitude). At 267 km, Bahamut is as tall as the state of Pennsylvania (longitudinally).

This is larger than any dragon we've ever seen before in the entire game. His father, Midgardsormr, is only about as massive as the Agrius airship, which can't be larger than an aircraft carrier. There are a few things that could account for this. First, my assumptions could be way off. Hydaelyn could be a much smaller planet; Menphina could be a much smaller moon; and Dalamud could be a much smaller satellite. There's really no way to tell. The only shot we've seen of the planet is this one:

Eorzea looks relatively Europe-sized, compared to the planet as a whole. That said, even if Hydaelyn were smaller than Earth, the proportion should still stay the same (i.e. his wingspan goes from Limsa to Gridania), unless that ratio is also way off. Bahamut the primal could also be much huger because of his status as a primal, whose power level corresponds to the amount of prayer and aether he's absorbed. As an elder primal who has absorbed energy from the sun for multiple millennia, it's possible that Bahamut's size increased proportionately.

Finally, to any enterprising Fermi estimationists, there are two other ways that we might calculate the size of Bahamut, perhaps more accurately. One, you could compare the width of the Dalamud fragment that impacted Carteneau in the End of an Era trailer with the known approximate height of the soldiers who are helpfully included in the shot for comparison. Then from there, calculate the size of Dalamud in Dalamud fragment-widths. Alternatively, you could estimate based on the size of Bahamut's claw, the battle arena of T5. It should be possible to measure the width of his hand in yalms and then scale that up to the size of his body and wingspan using the proportions above. Good luck!

[Anonymoose]

Bahamut is perhaps still the biggest dragon we've seen so far, but Merlwyb off-handedly compares his size to being roughly the same as an Eorzean city (the whole thing, I imagine, not just the parts we can wander), so the size of Penn. as a whole seems to be much too much. The palm approach seems like a good idea, but keep in mind that proportion and scale aren't always first on the dev. team's priorities and it might not all line up right, lol.

EDIT: Found it

From inside the shell of Dalamud came a winged nightmare—a dragon the size of a bloody city.

[dvoraen]

Keep in mind that Bahamut may well have been artificially inflated in size. The Final Coil of Bahamut kind of implies this. I'd say the 'real' Bahamut would have been about the size of the large dragon we see in the Tour of the North video.

[Cherub]

I'll allow myself to throw in my thoughts really quick. There is one thing I've been always wondering about. As we know Bahamut is a primal but there is the question of was he ever a dragon (and dragon only) or born a primal and if so, does him being a dragon (and dragon only) or being a primal change his size? not to mention how he became a primal but that's too crazy for me. Who knows maybe he isn't a primal after all. Maybe a crazy lalafell was the real bahamut.
We all know who phoenix is by now and mutation/transformation/power-uppu seems not out of question.
I can't really help out with the actual size guessing though but my 2 cents.

[Velox]

If you watch the end of an era video, you can see Bahamut briefly against the Limsa Lominsa backdrop. He is roughly right above the city, so using this as a scale it definitely supports the claims (and from what we saw in the Coils) that he is as big or slightly bigger than most Eorzean cities head-to-tail. Wingspan is much larger. Overall, he's monstrous in size.

Bahamut in life may have been much smaller. Remember that the primal-version is represented as how the Mercydian dragons imagined him (as is with all primals). It's true that Midgardsormr's children are definitely larger than most dragons we will encounter, but Bahamut's sheer size may only be due to the fact that he was reincarnated as a primal. Likewise, he may have always been unnaturally big. 3.0 should give us more story into the origins of dragon-kind and how they all relate to each other.

[treuhavik]

was he ever a dragon (and dragon only)

Yes.

does him being a dragon (and dragon only) or being a primal change his size?

We don't have hard information on this (primal inflation), but I'm 99.99% sure this is a "Yes" as well.

Midgardsormr's children are definitely larger than most dragons we will encounter

I'd hesitate to say anything definitively just yet, but Midgardsormr is likely slightly larger than his children and they all comparable in size to eachother. I also suspect that Vishap is much, much larger than the Dragons Seven based on the origin of his name.

[Cherub]

Yes.

I guess me wondering how he became a primal always lets me forget bout this fact.

We don't have hard information on this (primal inflation), but I'm 99.99% sure this is a "Yes" as well.

I wholeheartedly agree.

[myahele]

Yeah, I'm thinking that after thousands of years collecting aether/ energy that Calamity Bahamut became gigantic.

[axemtitanium]

Here's a screengrab of Bahamut flying past Limsa.

It's hard to tell exactly how big he is because he flies behind Limsa and there's no indication how far behind he flew (could be 300 fulms, could be 30,000 fulms, would contribute a big difference in estimated size). However, since he's farther behind Limsa, that puts a lower bound on his size as at least as big as Limsa castle and possibly much bigger. Multiple hundreds of meters tall at least.

An additional size data point could be the recreated Dalamud inside T11. Not sure if it's a full size replica (which would imply the the unfurled underground Binding Coils expanded larger than Dalamud itself) or a scale model. The platform Kaliya appears on is the "inner ball" that a curled up Bahamut with wings folded fit inside.

Another thing to note, Bahamut also flies from Carteneau to Limsa and back in a matter of seconds. If we maintain that Limsa > Gridania is 1600 km and Limsa > Carteneau is half that length, then a round trip would also be 1600 km. I didn't put a stopwatch to it, but he must have been flying at multiple hundreds of km/sec, which far outstrips the escape velocity of Earth (11.2 km/sec). Food for thought.

[ClaireAbigail]

The bahamut we faced in t13 is not the same as the one in the cinematic. Bahamut Prime is more than likely Elder bahamut's heart. I mean you can see his head in the end of t5,t9 and t12 it's huge.....not to mention t5 arena is bahamut's hand....