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How to use this calculator
Choose the formula (if there is more than one), choose what you want to find, then fill in the other values using the units shown. The calculator rearranges the formula, puts your numbers in, and shows every step.
How it's calculated
Newton's law of gravitation F = G m₁ m₂ / r², with G = 6.674 × 10⁻¹¹ N m²/kg². Field strength g = GM / r².
Worked example
Earth (5.97 × 10²⁴ kg) and a 70 kg person at 6.37 × 10⁶ m from its centre: F ≈ 687 N.
Frequently asked questions
How do I type very large numbers?
Use e notation: 5.97e24 means 5.97 × 10²⁴.
Is r the distance to the surface?
No. It is the distance between the centres of the two masses.
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Last updated October 2026. Results are for learning and guidance; always check important work. Calculations run in your browser and are not stored.