Space Physics: Escape Velocity, Orbits and Gravity Explained
The physics that governs rockets, satellites and stars — gravity, escape velocity, orbital speed, surface gravity, the scale of the cosmos and the strange mathematics of black holes.
Surface Gravity Calculator
Verified formula Updated Jun 2026 Private — runs on your device
Verified formula
Private
Surface gravity
9.820
- Compared to Earth (g)
- 1.001
For general information only — not financial, tax, legal or medical advice. Verify before you rely on it.
How to use the Surface Gravity Calculator
The Surface Gravity Calculator works out your surface gravity, along with 1 related figure in an instant. Enter mass of the body and radius and the result updates as you type — it is free, needs no sign-up, and runs entirely in your browser so your figures stay private.
- Enter the mass of the body.
- Enter the radius.
- Read off your surface gravity, together with compared to earth (g) — the calculator updates automatically, with no button to press.
Formula
The Surface Gravity Calculator uses the formula:
Surface gravity = 0.00000000006674 × Mass of the body ÷ (Radius × 1000) ^ 2
Worked example
For example, with mass of the body of 5,972,000,000,000,000,327,155,712 kg and radius of 6,371 km, the surface gravity is 9.820.
| Mass of the body | 5,972,000,000,000,000,327,155,712 kg |
|---|---|
| Radius | 6,371 km |
| Surface gravity | 9.820 |
|---|---|
| Compared to Earth (g) | 1.001 |
Results are estimates for educational use, not professional advice.
Key terms explained
- Radius
- The distance from the centre of a circle or sphere to its edge.
Frequently asked questions
Use g = GM ÷ r², with G the gravitational constant, M the mass and r the radius. Earth's values give about 9.82 m/s².
It is the acceleration due to gravity at a body's surface, which sets how much objects weigh there.
Expressing gravity as a fraction of Earth's 9.81 m/s² makes it easy to picture — for example, Mars is about 0.38 g.
Not always. Surface gravity depends on both mass and radius, so a large but low-density planet can have modest surface gravity.
Enter the mass of the body. Enter the radius. Read off your surface gravity, together with compared to earth (g) — the calculator updates automatically, with no button to press.
Related guides
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Weight on Other Planets Table: Weight on Mars by Your weight on Earth
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