Surface Gravity Calculator
Enter a body's mass and radius, or pick a preset, to find its surface gravity in metres per second squared and as a multiple of Earth's gravity.
How to use the surface gravity calculator
- Pick a planet preset or enter the body's mass in kilograms.
- Enter the radius in metres, measured from the centre to the surface.
- Read the surface gravity and how it compares to Earth's gravity.
Examples
Surface gravity of Earth
mass = 5.972e24 kg, radius = 6.371e6 m
g = about 9.82 m/s^2 (1.00 g)
Surface gravity of the Moon
mass = 7.342e22 kg, radius = 1.7374e6 m
g = about 1.62 m/s^2 (0.17 g)
Frequently asked questions
What is surface gravity?
Surface gravity is the gravitational acceleration felt by an object resting at the surface of a planet, moon or star. It sets how much things weigh there.
What is the surface gravity formula?
g = G x M / r^2, where G is the gravitational constant, M is the body's mass and r is its radius. Doubling the radius cuts gravity to a quarter.
Why is the calculated Earth gravity 9.82 and not 9.81?
Using a mean radius and ignoring rotation gives about 9.82 m/s^2. The standard 9.80665 m/s^2 includes the centrifugal effect of Earth's spin and an average over latitude.
Does surface gravity depend on the object resting on it?
No. The acceleration is the same for a feather or a boulder, so both fall at the same rate in a vacuum. Only the body's own mass and radius matter.
How does Moon gravity compare to Earth?
The Moon's surface gravity is about 1.62 m/s^2, roughly one sixth of Earth's. That is why astronauts could bound across the lunar surface.
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