Mean Earth–Moon Distance
| Value | 384,400,000 m |
| Status | Conventional / typical value |
| Source | NASA planetary fact sheet; Lunar Laser Ranging (semi-major axis) |
| Categories | Astronomicalsolar-systemmoon |
| femtometer | 3.8440000e+23 fm |
| picometer | 3.8440000e+20 pm |
| nanometer | 3.8440000e+17 nm |
| micrometer | 384,400,000,000,000 μm |
| millimeter | 384,400,000,000 mm |
| centimeter | 38,440,000,000 cm |
| decimeter | 3,844,000,000 dm |
| meter | 384,400,000 m |
| kilometer | 384,400 km |
| inch | 15,133,858,000 in |
| foot | 1,261,154,900 ft |
| yard | 420,384,950 yd |
| mile | 238,855.09 mi |
| nautical mile | 207,559.4 nmi |
| astronomical unit | 0.0025695553 AU |
| light-year | 4.0631112e-08 ly |
| parsec | 1.2457556e-08 pc |
Learning zone
Hipparchus estimated the Moon's distance in the second century BC at about 60 Earth radii, using the size of Earth's shadow during a lunar eclipse — the first correct measurement of any distance beyond our planet, and remarkably close to the true 60.3. Today the answer comes from bouncing laser pulses off the retroreflector arrays left by Apollo 11, 14 and 15 and by the Soviet Lunokhod rovers, timing the two-second round trip to millimetre precision.
Those same measurements show the Moon receding by 3.8 cm a year, as tidal bulges on Earth drag ahead of the Moon and transfer angular momentum outward — the flip side of the day lengthening. Because the orbit is an ellipse with eccentricity 0.055, the distance swings by 50 000 km, which is what makes some total eclipses annular and gives the popular "supermoon" its extra 14 per cent in apparent diameter.