How small could the Great Spirit Robot be?

The Great Spirit Robot is an immense robot, boasting an astonishing canon height of approximately 12,200 km (7,600 mi / 40,000,000 ft), implying that Mata Nui is nearly Eart-sized. I believe we can all agree that this value has never made sense, considering that the island of Mata Nui, which is 486 km (302 mi) in length and 285 km (177 mi) wide, is the size of the GSR face. Faberfiles show a more coherent size, indicating that the GSR stands at 3,300 km (2,000 mi) in height—roughly the size of the Moon.

However, this size still appears disproportionate when considering events like the battle at Bara Magna and other visual references. So, let’s explore how small the GSR could be while still accommodating an entire universe within it.

First let’s examine Aqua Magna. This moon had liquid water on its surface, with temperatures and pressures that seemed akin to Earth’s tropical regions. This suggests that Aqua Magna has the same mass, size, and atmosphere with Earth.

Considering that the robot was fully submerged (except for his face), and drawing a parallel with Earth’s oceans, which have an average depth of 3,900 m (130,000 ft), the GSR would need to have a height of 24 km (15 mi) (and bend his feet to the sides). Although this is undeniably massive, it doesn’t seem to be able to house all the islands and inhabitants within the robot. Therefore, Aqua Magna’s ocean are significantly deeper than those on Earth.

Mata Nui under water

In his comic book appearance, the GSR appears to be “crossing” the atmosphere of Aqua Magna while standing. Earth’s atmosphere doesn’t actually have a definitive line where it ends, where its last layer, the exosphere, reach up to 10,000 km from sea level. However, what is represented in the images is more likely the “blue halo” around the Earth, which is limited by the Kármán line, which is about 100 km (62 mi) above sea level. Based on the image in the comic, this would give the GSR a height of 210 km (130 mi).

Not bad, but let’s not forget that Mata Nui’s inspiration was the human body, where the Toa were the immune system fighting disease. The closest thing to a Toa would be a T-cell, which is about 8 μm in size, about 220,000 times smaller than a human. Toa height is approximately 2.2 m (7.2 ft), so following this logic the GSR should measure about 480 km (300 mi).

Would Metru Nui fit on this robot’s head? No. Metru Nui is 65 km (41 mi) in length, whereas the head of this robot would only be around 40 km. But Metru Nui doesn’t need to be that big, especially considering its low population. In my opinion, with 15 km (9.3 mi) in length and 7.5 km (4.7 mi) wide, the city should be big enough to justify the existence of the Chute System as a method of transportation. With this size it would fit in the head. But the island is contained in a dome, surrounded by the Silver Sea. If the dome had a circular base, it wouldn’t leave much space between the island and the Great Barrier. Therefore, the GSR would need to be about twice as big, with 850 km (530 mi) in height, to fit well the city.

At this size, the island of Mata Nui would measure 95 km (59 mi) in length and 50 km (31 mi) wide. This would also make Mangai Volcano crater around 2 km (1.2 mi) in diameter, quite large for a stratovolcano. Could an island of this size have such a varied landscape? I don’t know, I don’t even know if the original size island was capable of that. I blame the Energized Protodermis.

If we measured the size of the islands on the Matoran Universe map in relation to Metru Nui, the smallest islands would have a diameter of around 5 km (3.1 mi), like some Polynesian islands. It may sound small, but the truth is that most islands appear to be just a fortress. In that regard, the islands of the Matoran Universe could be distributed in this way:

Comparing with the other sizes it would look something like this:

I know it’s not as impressive in comparison, but he’s still incredibly huge. Earth’s atmosphere would barely reach his feet.

But if the GSR were that small, couldn’t Voya Nui be seen from Mata Nui? In this scenario they would be around 150 km (93 mi) apart, so I don’t know, I hope not. But with this size, the GSR would look like Goku on Planet Kaio.

TL;DR: 850 km (530 mi) in height


I’m pretty sure that the planet was mostly made of water.

While this may be the smallest physical size in terms of cramming all the islands inside, there are plot threads that hinge on it being much larger. For example, Icarax once tried taking over the Matoran Universe starting from Karzahni while Teridax was stuck in the Toa Metru’s Toa Seal. If the universe was this small, taking it over would be extremely easy for him.

Overall, though, this is still a really good analysis. My point above is ultimately useless, since we already know the actual size, and this still does a great job of finding the absolute lower limit.


Mata Nui crash landed over something. Even gas giants have a solid core, so most probably Aqua Magna also had a solid core and wasn’t just water. Even with the GSR canon size, most of Aqua Magna should have been a rocky core surrounded by a lot of water.

About Icarax, size shouldn’t be a problem, considering that he can just teleport. And six Matoran were able to arrive to Karzahni from Metru Nui. So why didn’t Icarax take over the Matoran Universe? Maybe he was just lazy.


Yeah, that’s what I was thinking; the whole thing could be relatively small with ridiculously deep oceans.


Honestly, this is really good analysis and just how off the writers’ sense of scale was.

Another thing I’d like to see tackled is scale of Bara Magna. If we were to take Greg’s height of MN at face value, then Aqua Magna would need to larger than Earth, and thus Spherus Magna the size of a gas giant.


Since art depictions aren’t consistent, it’s hard to say that Aqua Magna was bigger than Earth. Mata Nui could simply had had a very bendy back.

RahiWatching made an interesting investigation about Spherus Magna system here, but he conclude that Aqua Magna is smaller than Earth and Bara Magna is slighly bigger. But Rahi used Faber size. With the canon size, Bara Magna should be 1.77x larger than Jupiter.