Australia vs The Moon: bigger by how much?
Australia measures 4,036 km (2,508 mi) east to west, and the Moon measures 3,475 km (2,159 mi) across. That puts Australia at 1.16 times the measured size of the Moon: 560.8 km (348.4 mi) of difference, 16%. The two are not judged on the same axis: Australia is quoted as an east-west span and the Moon as a diameter, so the honest statement is one figure against the other, 86% of it, and not one outline against another. Australia and the Moon are both written in thousands of kilometres, and the 16% between them is the whole of the difference.
| Object | Real size | Axis measured | What the figure covers |
|---|---|---|---|
| Australia | 4,036 km 2,508 mi |
East-west span | Country |
| The Moon | 3,475 km 2,159 mi |
Diameter | Widest extent of the outline on that axis |
Both figures, Australia and The Moon, come from the Size It Up measurement set, one real-world size and one measured axis per object, last checked in September 2026; outline provenance is listed on the sources page.
Why this one is hard to judge by eye
The outline of Australia that most people carry comes from a world map, and every projection that keeps angles true stretches whatever sits far from the equator; the outline of the Moon above is scaled from measured distances instead. A gap of 16% is invisible without a shared baseline: on the ground line above, the Moon stops 560.8 km (348.4 mi) short of Australia.
What each figure covers
Australia. Australia is measured east to west across the mainland outline. On most world maps it looks smaller than Greenland, which is an artefact of the projection rather than a fact about either.
The Moon. The Moon is given as a mean diameter, because it is very slightly out of round. It is about a quarter of Earth by diameter, which is unusually large for a moon.
Australia is quoted as an east-west span and the Moon as a diameter: two conventions, so the ratio compares the two numbers rather than the two objects.
What else is about that size?
Measured the same way, Australia at 4,036 km sits within a tenth of Brazil at 4,308 km and Alaska at 3,636 km. Swapping any of those in for Australia would move its ratio to the Moon by less than 10%.