How to Calculate Gravity on Another Planet
Surface gravity g = GM/R² explained, plus weight and escape velocity. Worked examples for Earth, the Moon and Mars, and why gas giants have no surface.
The idea behind it
A planet’s mass increases its pull, while a larger radius puts its surface farther from the center. Your mass stays the same on another world; your weight, a force measured in newtons, changes.
The relationship to remember
At 1 Earth masses and 1 Earth radii: weight = 70 kg × 9.82 m/s² = 687.42 N.
Make your own discovery
Double the radius while keeping the mass fixed. Surface gravity falls to one quarter of its original value.
Open the Planetary Gravity & Escape Velocity Calculator ↗Key formulas
| Quantity | Formula | Note or example |
|---|---|---|
| Surface gravity | g = GM / R² | M = mass, R = radius |
| Scaling from Earth | g ≈ 9.82 m/s² × (M / M⊕) ÷ (R / R⊕)² | Masses and radii in Earth units |
| Weight | W = m × g | Newtons; your mass m stays the same |
| Escape velocity | vₑ = √(2GM / R) | Earth ≈ 11.2 km/s |
Worked examples
Each row uses one of this lab’s presets and the same model as the interactive tool.
| Example | Surface gravity | Your weight | Escape speed |
|---|---|---|---|
| Earth | 9.82 m/s² | 687.42 N | 11.19 km/s |
| Moon | 1.62 m/s² | 113.7 N | 2.38 km/s |
| Mars | 3.73 m/s² | 261.1 N | 5.03 km/s |
What this model leaves out
A spherical, non-rotating body without atmospheric drag. Radius means distance from the center to the reference surface. Gas giants do not have a solid surface to stand on.
Check your understanding
What is the difference between mass and weight?
Mass measures the amount of matter in kilograms. Weight is gravitational force, measured in newtons.
Does escape speed depend on spacecraft mass?
In this ideal model, no. It depends on the attracting world’s mass and the starting distance from its center.
How do you calculate gravity on another planet?
Divide the planet’s mass (in Earth masses) by the square of its radius (in Earth radii), then multiply by Earth’s gravity, about 9.8 m/s². For Mars: 0.107 ÷ 0.532² × 9.8 ≈ 3.7 m/s².
Continue with the formula reference or test yourself in space practice.