Find the gravitational attraction between two masses with Newton's law F = G·m₁m₂/r² — or solve for a mass or the distance. Use kilograms and metres, or astronomy units like solar masses and AU.
Newton's law of universal gravitation says every mass attracts every other mass with a force proportional to the product of their masses and inversely proportional to the square of the distance between their centres: F = G·m₁m₂/r², with G = 6.674×10⁻¹¹ N·m²/kg².
Because it is an inverse-square law, doubling the distance quarters the force. Gravity is extremely weak between everyday objects but dominates on astronomical scales, holding planets, stars and galaxies together.
It states that the gravitational force between two masses is F = G·m₁m₂/r² — proportional to both masses and inversely proportional to the square of the distance between them.
G ≈ 6.674×10⁻¹¹ N·m²/kg². It sets the strength of gravity and is one of the most fundamental constants in physics.
Force follows an inverse-square law: doubling the separation reduces the force to a quarter, and tripling it to a ninth.
Because G is tiny. Two 1 kg masses 1 m apart attract with only about 6.7×10⁻¹¹ N — undetectable without sensitive instruments. Gravity only becomes strong with astronomical masses.