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Planetary Gravity Calculator

Work out planetary gravity instantly with clear inputs, formula shown and shareable results.

About Planetary Gravity Calculator

Surface gravity is GM/R^2, so it depends on mass and radius together rather than mass alone. Mars, at 0.107 Earth masses but only 0.532 Earth radii, has 3.71 m/s2 - 38% of Earth's - and an escape velocity of 5.0 km/s. That low escape velocity is why Mars lost most of its atmosphere.

Formulas

Surface gravity

g = G M / R^2

Escape velocity

v = sqrt(2 G M / R)

Worked example

With the default values below, Planetary Gravity Calculator returns Surface Gravity of 3.713. Change any input above and every figure here is recalculated in your browser.

Inputs used

Planet massminimum 0 Earth masses
0.107 Earth masses
Planet radiusminimum 0 Earth radii
0.532 Earth radii
Mass of an object to weighminimum 0 kg
70 kg

Results

Surface Gravity
3.713 m/s2
Gravity Relative To Earth
0.3786
Weight Of The Object There
259.9 N
Escape Velocity
5.017 km/s

Step by step

  1. 1Values used
  2. 2Surface gravity
  3. 3Escape velocity
  4. 4Surface Gravity= 3.713 m/s2
  5. 5Gravity Relative To Earth= 0.3786
  6. 6Weight Of The Object There= 259.9 N
  7. 7Escape Velocity= 5.017 km/s

Assumptions and limits

  • The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Why is Mars gravity 38% of Earth's when its mass is only 11%?

Because its radius is also much smaller, and the inverse square on radius partly compensates for the lower mass.

Which planet has surface gravity closest to Earth's?

Venus, at 8.87 m/s2 or 90% of Earth's, thanks to a similar mass and radius.

Related Calculators

Planetary Gravity Calculator – Calculate Surface Gravity