Planetary Surface Gravity Calculator

Surface gravity is the gravitational acceleration at the surface of a planetary body.

Formula:

g = GM / R²

Where:

• G = 6.674 × 10⁻¹¹ N·m²/kg²
• M = mass of the body (kg)
• R = radius of the body (m)

Surface gravity around the Solar System:

Every row is what the calculator below prints, so the table, the dropdown and the chart cannot disagree with each other.

Why Earth reads 9.82 here and 9.81 everywhere else. The famous 9.80665 m/s² is standard gravity, defined at about 45 degrees latitude at sea level, and it already has the centrifugal effect of Earth’s rotation subtracted out. GM/R² with the mean radius gives 9.8195, which is the pure gravitational figure with nothing removed. Most of that 0.13% gap is the spin, and the rest is the difference between a perfect sphere and the real, slightly flattened Earth. Every body in the table is quoted the same way, without rotation, so the comparisons between them are apples to apples.

Which radius the gas giants use, and why it matters: The four giant planets have no surface to stand on, so “surface gravity” is quoted at the altitude where the atmospheric pressure reaches one bar, using the equatorial radius. That convention is worth stating because these planets are visibly squashed by their own rotation. Jupiter’s equatorial radius is 71,492 km while its polar radius is only 66,854 km, a 7% difference, and gravity goes as 1/r². Feed the mean volumetric radius into the formula instead and you get 25.92 m/s² for Jupiter rather than 24.78, which is where a lot of the disagreement between published tables comes from. The rocky bodies and Pluto use their mean radii, since they are close enough to spherical that it makes no visible difference.

You will also see Uranus listed as 8.69 rather than 8.87, and that is not a radius argument at all. It is the effective gravity, meaning what a scale would read, with the planet’s rotation taken off. Uranus turns once in 17.2 hours and the centrifugal term costs it about 2%. Saturn is the extreme case: 10.44 by the formula, 8.96 effective, a 14% difference, because it spins in 10.7 hours and is barely denser than water. This calculator reports the formula value in every case.

Note the coincidence in the table: Venus and Uranus have almost exactly the same surface gravity, despite Uranus being nearly eighteen times more massive. Uranus is simply so much larger and less dense that the two cancel out.

Weight calculation: Weight = mass × g

On Mars, a 70 kg person weighs 26.6 kg-equivalent and could jump about 2.6× higher. On Jupiter’s cloud tops the same person weighs 176.7 kg-equivalent and could barely stand.

Note on “weight on other planets”: The mass of a person, in kg, never changes. Only their weight, in Newtons, changes. We convert back to “kg-equivalent” by dividing the force by Earth’s own GM/R² of 9.8195 m/s², which is the same figure the table uses, so Earth comes out at exactly 1.000×.