Surface Gravity Calculator

Surface gravity is the gravitational acceleration experienced at the surface of a planet or other body, denoted g. It is calculated as g = GM/r², where G is the universal gravitational constant (6.674 x 10^-11 N m²/kg²), M is the body's mass (kg), and r is its mean radius (m). Earth's surface gravity is approximately 9.81 m/s².

Earth is not a perfect sphere: it bulges at the equator and flattens at the poles. Equatorial radius is 6,378 km and polar radius is 6,357 km. Since g = GM/r², the poles are closer to the center and have slightly higher gravity (9.832 m/s²) than the equator (9.780 m/s²). Altitude also reduces g.

The Moon's surface gravity is about 1.62 m/s², which is roughly 1/6 of Earth's. This is why astronauts on the Moon could jump much higher and why objects fall more slowly there. The Moon's mass is 7.342 x 10^22 kg and its mean radius is 1,737.4 km.

Yes. Jupiter's surface gravity is about 24.8 m/s² (2.53 g), and a human on Jupiter would feel about 2.5 times heavier than on Earth. Neutron stars have surface gravities of about 10^11 to 10^12 m/s², so extreme that a fallen object would hit the surface in microseconds.

For a uniform sphere, g = GM/r² exactly. For a non-uniform body you need to know the mass distribution. For practical calculations using planetary averages, the formula g = GM/r² with the mean radius gives a useful approximation of the average surface gravity.