Gravitational Force Calculator
Find the gravitational attraction between two masses.
Results update as you type.
How it works
Gravitational force is the universal attraction that pulls any two masses toward each other, and this gravitational force calculator finds it from the two masses and the distance separating their centres. From the falling of an apple to the orbits of planets, the same law governs them all: every object with mass tugs on every other, with a strength that grows with the masses and weakens sharply as they move apart. This calculation matters far beyond the classroom. It explains why the Moon orbits the Earth, why you weigh slightly less on a mountaintop, and how spacecraft are steered using the pull of distant worlds. Because the force depends on the product of the masses and the square of the distance, small changes in separation have a large effect, which the calculator makes easy to explore without wrestling with the tiny gravitational constant by hand. The law works because gravity spreads out over the surface of an expanding sphere, so its strength falls with the square of the distance, while doubling either mass simply doubles the pull. Physics students, astronomy enthusiasts, and engineers planning orbits all rely on a gravitational force calculator to turn masses and a distance into a precise force in newtons using Newton's famous equation.
F = G × mass₁ × mass₂ ÷ distance²
Newton's law of gravitation multiplies the two masses together, divides by the square of the distance between their centres, and scales the result by the gravitational constant G, about 6.674 times ten to the minus eleven. The masses multiply because each attracts the other, and the distance is squared because gravity weakens over the growing surface of a sphere as it spreads outward from a mass into space.
Source:Standard physics (Newton's law of gravitation)
We review all our tools from time to time to ensure accuracy.
Worked example
How to use this calculator
- 1
Enter your values
Enter first mass, second mass and distance between centres.
- 2
Adjust the options
Fine-tune any options to match your situation.
- 3
Read your result
Gravitational force updates instantly as you type — no button to press.
Frequently asked questions
What units should I enter?
Use kilograms for both masses and metres for the distance between their centres, and the force comes out in newtons. The gravitational constant built into the calculator assumes these SI units, so mixing in grams or kilometres would throw the result off by large factors. Convert any non-standard units first: one tonne is a thousand kilograms, and one kilometre is a thousand metres, keeping every figure consistent.
Why is the gravitational force usually so small?
Gravity is by far the weakest of the fundamental forces, and the gravitational constant is extremely tiny, around 6.674 times ten to the minus eleven. As a result, everyday objects attract each other with forces far too small to feel. Gravity only becomes noticeable when at least one mass is enormous, like a planet or a star, which is why we sense Earth's pull but not a nearby building's.
How does distance affect the force?
The force follows an inverse-square law, so it weakens with the square of the distance between the masses. Double the separation and the force drops to a quarter; triple it and the force falls to a ninth. This rapid decline explains why gravity, though infinite in range, becomes negligible over large distances, and why proximity matters so much when comparing the pull between orbiting bodies.
Does this measure the distance between surfaces or centres?
Newton's law uses the distance between the centres of mass of the two objects, not the gap between their surfaces. For spherical bodies like planets, the entire mass acts as if concentrated at the centre, so you measure from centre to centre. When finding your weight on Earth, for example, the distance is the planet's radius, not your height above the ground.
Can I use this to find my weight?
Yes. Enter your mass, the Earth's mass of about 5.97 times ten to the twenty-fourth kilograms, and the Earth's radius of roughly 6,371,000 metres, and the force returned is your weight in newtons. The result matches multiplying your mass by 9.81, the familiar gravitational acceleration, because that acceleration is itself derived from this same law applied at the Earth's surface.