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Gravity calculator
Calculate weight on a planet or the gravitational force between any two masses.
Universal Gravity
F = GMm/r² · Force · Mass · Distance
Weight: F = m × g | Universal: F = G × M × m / r²
Newton's law of gravitation says every pair of masses attracts, with a force growing with both masses and collapsing with distance squared. This calculator computes that force between any two objects you describe.
How to use this calculator
- Enter the two masses.
- Enter the distance between their centres.
- Press calculate to see the gravitational force in newtons.
Weak force, enormous masses
Run two people, or even two cars, through the formula and the attraction is vanishingly small, far below friction's notice. Gravity rules the universe only because planets and stars pile up so much mass, and because nothing cancels it: there is no negative mass shielding the pull.
Frequently asked questions
What is the gravitational force formula?
F = G × m1 × m2 / r², where G is the gravitational constant (about 6.674 × 10⁻¹¹), the masses are in kilograms and r in metres.
What does inverse-square mean in practice?
Double the distance and the force falls to a quarter; triple it, to a ninth. Distance punishes gravity quickly, which is why the (much nearer) Moon raises tides over the (far stronger-pulling) Sun.
Is the gravity on the Moon one-sixth of Earth's?
At its surface, roughly yes, because the Moon has less mass and a smaller radius. The same formula, with the Moon's figures, gives its surface gravity directly.