How big was Ancalagon the Black?

So, you've read about Ancalagon the Black, and you’ve read that he was big–really big. But a small part of you wonders: just how big was he?

If you haven't read about Ancalagon before, he was the largest and greatest of all winged dragons in Tolkien's Middle-Earth, bred by Morgoth during the First Age.

And honestly, I don’t think even Tolkien himself knew how big Ancalagon the Black was! He just wanted to make sure you felt Ancalagon was bigger than your scariest nightmares. But since you care so much about the size of this dragon (I always heard size didn’t matter?), I'm here to help you imagine him better for your next fantasy.

Let's first look at the few times Tolkien mentioned Ancalagon:

"Then, seeing that his hosts were overthrown and his power dispersed, Morgoth quailed, and he dared not come forth himself. But he loosed upon his foes the last desperate assault that he had prepared, and out of the pits of Angband there issued the winged dragons, that had not before been seen; and so sudden and ruinous was the onset of that dreadful fleet that the host of the Valar was driven back, for the coming of the dragons was with great thunder, and lightning, and a tempest of fire."

So, understanding that Ancalagon was the first dragon, and led the winged dragons mentioned above, now we’ve learned that Ancalagon must have been able to fit in the pits of Angband! Which begs another question, how big were those pits? And of course, there are no specific dimensions given for these either. We do know that Angband was a sprawling, huge underground complex. It's also worth noting that Morgoth was fully capable of changing the growth and size of a creature, so it's conceivable that Ancalagon the Black was actually bigger than the pit, but Morgoth forced him into it by making him smaller (not sure if Ancalagon would have given his consent, but Morgoth was the villain anyway).

"It has been said that dragon-fire could melt and consume the Rings of Power, but there is not now any dragon left on earth in which the old fire is hot enough; nor was there ever any dragon, not even Ancalagon the Black, who could have harmed the One Ring, the Ruling Ring, for that was made by Sauron himself." [LotR, i, 2, 'The Shadow of the Past']

In the paragraph above, Tolkien did not mention Ancalagon’s size but rather his inability to destroy the One Ring, even though Ancalagon had the hottest fire of any dragon in history. (I know, it's a tangent but it’s cool so I'm telling you.) Let’s check the other time he mentioned Ancalagon:

"Before the rising of the sun, Eärendil slew Ancalagon the Black, the mightiest of the dragon-host, and cast him from the sky; and he fell upon the towers of Thangorodrim, and they were broken in his ruin." [The Silmarillion, 24, 'Of the Voyage of Eärendil and the War of Wrath'] and remote account of the end of the First Age, when Thangorodrim was broken and Morgoth overthrown; [The Silmarillion, 'Foreword']

In this paragraph, Tolkien refers to Ancalagon as the mightiest in the army of dragons. But the word mighty is subjective and could refer to physical power, battle prowess, inherent magical ability, or any number of other attributes. The second part of the paragraph is more helpful as we are told that Ancalagon was "cast from the sky" and "fell upon the towers of Thangorodrim," breaking them in his ruin. Now we have a new problem: we don’t know how big the towers were! Let’s take a look at some more things Tolkien wrote about Thangorodrim and see if we can unravel this:

"And [Morgoth] being freed gathered again all his servants that he could find, and came to the ruins of Angband. There he delved anew his vast vaults and dungeons, and above their gates, he reared the threefold peaks of Thangorodrim, and a great reek of dark smoke was ever wreathed about them." [ibid, Ch. 9, 'Of the Flight of the Noldor']

"But Morgoth, as has been told before, returned to Angband, and built it anew, and above its doors, he reared the reeking towers of Thangorodrim." [ibid., Ch. 10, 'Of the Sindar']

"…with his last sight [Fëanor] beheld far off the peaks of Thangorodrim, mightiest of the towers of Middle-earth…" [ibid., Ch. 13, 'Of the Return of the Nodor']

"Beneath Ered Engrin [Morgoth] made a great tunnel, which issued south of the mountains; and there he made a mighty gate. But above this gate, and behind it even to the mountains, he piled the thunderous towers of Thangorodrim, that were made of the ash and slag of his subterranean furnaces, and the vast refuse of his tunnellings. They were black and desolate and exceedingly lofty; and smoke issued from their tops, dark and foul upon the northern sky." [ibid., Ch. 14, 'Of Beleriand and its Realms']

Most passages refer to Thangorodrim as towers, but some also call them ‘peaks’. Either way, there are still no clues how big the Thangorodrim were, but if we imagine they actually were towers the size of mountain peaks, as Tolkien seems to hint at, what does that suggest? That Ancalagon the Black destroyed the equivalent of three mountain peaks under his weight when he fell on them.

Taking this idea further and going full-nerd on it, according to The InternetTM the amount of energy needed to destroy one mountain is approximately 22.075 megatons of TNT. If we assume Ancalagon was 20,000 feet above the peaks (which is a reasonable assumption, given the sheer scale of Ancalagon and of mountains), to find his mass we only need to put some numbers in this formula: Force = Mass x Gravity x Height, and then multiply it by 3 for the 3 peaks.

22,075,000,000 = M * 9.8 * 20,000, or M = 22,075,000,000 ÷ 20,000 ÷ 9.8

So M = 112,627.5 tons

Multiplied by three, that's 337,882.5 tons—potentially the mass required for Ancalagon the Black to destroy three mountain peaks. Given this immense weight, Ancalagon must have been composed of something other than just bone and muscle, as a creature made solely of those materials with this mass would be larger than Earth itself.

For reference, that's more than the weight of three US aircraft carriers . If we stacked all three on top of each other, it would roughly match the size of Ancalagon the Black with his wings folded. One aircraft carrier is 244 feet tall, 1,100 feet long, and 250 feet wide. So, Ancalagon the Black would be approximately 733 feet tall, 1,100 feet long, and 250 feet wide—30 times taller and almost 10 times longer than Smaug.

But this is just a bit of fun having a guess, and that’s all it will ever be. Suffice to say, Ancalagon was really, really big–mountainously big.