Mass of the Moon
| Value | 7.3459e22 kg |
| Status | Measured: ± 1.60e+18 kg (0.000022 relative) |
| Source | NASA planetary fact sheet; GM from GRAIL divided by CODATA 2022 G |
| Categories | Astronomicalsolar-systemmoon |
| microgram | 7.3459000e+31 μg |
| milligram | 7.3459000e+28 mg |
| gram | 7.3459000e+25 g |
| kilogram | 7.3459000e+22 kg |
| metric tonne | 7.3459000e+19 t |
| ounce | 2.5911900e+24 oz |
| pound | 1.6194937e+23 lb |
| stone | 1.1567812e+22 st |
| US short ton | 8.0974687e+19 ton |
| grain | 1.1336456e+27 gr |
| unified atomic mass unit (dalton) | 4.4238044e+49 u |
Learning zone
The Moon is anomalously heavy for a satellite: 1/81.3 of its planet, where Jupiter's largest moon is under 1/12 000 of Jupiter. That ratio, together with the Moon's iron-poor composition and the identical oxygen-isotope signature of lunar and terrestrial rock, is the core evidence for the giant-impact hypothesis — a Mars-sized body striking the young Earth and splashing mantle material into orbit.
The mass is known from spacecraft tracking of GM, refined enormously by the twin GRAIL orbiters in 2012, which mapped the lunar gravity field to a precision no other body including Earth can match. The system's mass distribution is close enough to shared that Earth and Moon orbit a common barycentre 4670 km from Earth's centre — still 1700 km beneath the surface, but only just.