Enter mass and radius for any planet. See gravity, weight change, density, and escape speed. Export results, inspect trends, and learn the governing formula.
| Planet | Mass (10²⁴ kg) | Mean Radius (km) | Surface Gravity (m/s²) | Earth Relative |
|---|---|---|---|---|
| Mercury | 0.3301 | 2,439.7 | 3.702 | 0.377 g |
| Venus | 4.8675 | 6,051.8 | 8.87 | 0.905 g |
| Earth | 5.9722 | 6,371 | 9.82 | 1.001 g |
| Mars | 0.6417 | 3,389.5 | 3.728 | 0.38 g |
| Jupiter | 1,898.13 | 69,911 | 25.92 | 2.643 g |
| Saturn | 568.34 | 58,232 | 11.186 | 1.141 g |
The main surface gravity formula is g = GM / r². Here, G is the gravitational constant, M is planet mass, and r is the distance from the planet center. For surface gravity, use the mean planet radius.
For altitude, the calculator uses g(h) = GM / (R + h)². Escape velocity uses v = √(2GM / r). Circular orbital velocity uses v = √(GM / r). Average density uses mass divided by sphere volume.
If you enter a rotation period, the page also estimates equatorial reduction with geffective = g - ω²R. That correction is strongest for rapidly rotating planets and is most useful for comparing equatorial conditions.
Planet surface gravity describes how strongly a planet pulls objects toward its center at the surface. It is a basic result in mechanics, astronomy, planetary science, and spacecraft mission planning. Mass increases gravity, but a larger radius spreads that mass farther from the surface and weakens the pull.
This is why a very large world does not always create extreme surface gravity. Radius matters just as much because gravity changes with the square of distance. The calculator makes that relationship practical by letting you test custom planets, well known planets, and altitudes above the surface.
Students can use the page to compare planets and check homework steps. Teachers can use it to show how scaling works across the Solar System. Space and science readers can estimate escape velocity, orbital speed, average density, and weight changes for a person or payload.
The altitude feature is useful for satellites, mountain elevations, and thought experiments about high flight or hovering stations. The rotation option adds another layer by estimating how spin slightly reduces effective gravity at the equator. Together, these outputs give a broader physical picture than a single gravity value alone.
Surface gravity is the acceleration caused by a planet's gravity at its surface. It tells you how quickly objects fall and how heavy they feel compared with the same mass on another world.
Mass controls gravitational strength, while radius controls distance from the planet center. A large radius can reduce surface gravity even when total mass is high, so both values are necessary.
The calculator increases the distance from the planet center. Because gravity follows an inverse square relation, the value decreases as altitude rises above the surface.
No. Mass stays constant, but weight changes with local gravity. If you enter body mass, the calculator estimates how much force gravity would apply and the matching scale reading.
Rotation creates a small outward effect at the equator. Fast spin reduces effective gravity there, so the optional rotation field helps you estimate a more realistic equatorial value.
Use the mean radius unless a problem specifically asks for equatorial or polar radius. Mean radius gives a balanced estimate for general physics calculations and comparisons.
Yes. If you know an exoplanet's estimated mass and radius, you can enter those values directly. The results are only as reliable as the underlying measurements.
They help connect surface gravity to broader orbital physics. Escape velocity shows how hard it is to leave the planet, while orbital speed shows how fast a circular orbit must move.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.