What is the Moon's equatorial circumference?

The Moon’s equatorial circumference is about 10,921 kilometers.

Equatorial circumference is the distance around the Moon along its equator, the widest latitude circle. It is calculated from the Moon’s equatorial radius using the circle formula 2πr; with an equatorial radius of roughly 1,738.1 km, the result rounds to about 10,921 km.

This is not the same as the Moon’s polar circumference or a route measured over its irregular, cratered terrain. The Moon is slightly flattened and has a small equatorial bulge, so its equatorial and polar dimensions are not identical. Reference tables therefore specify which circumference they mean.

The number is roughly one-quarter of Earth’s equatorial circumference, which is about 40,075 km. A common mix-up is 6,792 km, the approximate circumference of Mars, or 21,344 km, which is not the Moon’s circumference. The Moon’s diameter across the equator is about 3,476 km.