Explanation and example

Newton’s law of universal gravitation is F = G × m₁ × m₂ / r². Enter masses in kilograms and centre-to-centre distance in metres; force is reported in newtons. We use the CODATA 2022 recommended value G = 6.67430 × 10⁻¹¹ m³/(kg·s²).

Example: two 1000 kg bodies whose centres are 1 m apart attract with approximately 0.000066743 N. Doubling the distance reduces the force to a quarter. This inverse-square check is useful when assessing whether inputs are in the right units.

Limits

The equation describes point masses and approximates spherically symmetric bodies. Close irregularly shaped bodies may require a more detailed model. Measure between centres, not surfaces, and do not confuse this force directly with ordinary weight near Earth.