Mean Radius of Mars
| Value | 3,389,500 m |
| Status | Measured: ± 200 m (0.000059 relative) |
| Source | NASA planetary fact sheet (volumetric mean radius) |
| Categories | Astronomicalsolar-systemplanets |
| femtometer | 3.3895000e+21 fm |
| picometer | 3.3895000e+18 pm |
| nanometer | 3.3895000e+15 nm |
| micrometer | 3,389,500,000,000 μm |
| millimeter | 3,389,500,000 mm |
| centimeter | 338,950,000 cm |
| decimeter | 33,895,000 dm |
| meter | 3,389,500 m |
| kilometer | 3,389.5 km |
| inch | 133,444,880 in |
| foot | 11,120,407 ft |
| yard | 3,706,802.3 yd |
| mile | 2,106.1377 mi |
| nautical mile | 1,830.1836 nmi |
| astronomical unit | 0.000022657408 AU |
| light-year | 3.5827043e-10 ly |
| parsec | 1.0984621e-10 pc |
Learning zone
Mars is about half Earth's radius and, like Earth, is flattened by rotation — its day is only 40 minutes longer than ours. But the ellipsoid is a poor description of the real surface, because Mars has the most extreme topography of any rocky planet: Olympus Mons rises 22 km above the datum, and the Tharsis bulge lifts a continent-sized region several kilometres, while Hellas basin sinks 7 km below. There is no sea level to reference, so the datum is defined by a chosen mean-pressure surface and a gravity model.
The northern lowlands sit on average 5 km below the southern highlands — the Martian dichotomy, plausibly the scar of an enormous early impact. The mean radius still gives a useful surface area, about 145 million km², almost exactly the land area of Earth.