Gravity Calculator

Three gravity questions worked from Newton's law. The first tab takes two masses and the distance between their centres and returns the force between them and the acceleration each one feels. The second takes a mass and a radius and gives the surface gravity, the escape velocity and the mean density that implies. The third takes a central mass and an orbit radius and returns the orbital speed, the period and the escape velocity there. Masses and distances can be entered in Earth masses, solar masses, Earth radii, astronomical units and light years as well as SI units.

Calculator Type

First Mass Measured In

Second Mass Measured In

Distance Measured In

Newton's law of universal gravitation. Centre to centre distance, not surface to surface.

First Mass (kg) *

Second Mass (kg) *

Distance Between Their Centres (m) *

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Mass Measured In

Radius Measured In

What g is at the surface of a body, and how fast you would have to leave it to never come back.

Mass of the Body (Earth masses) *

In whichever unit you pick beside the box. For Earth, enter 1 and pick Earth masses.

Radius of the Body (km) *

Your Own Mass (kg, optional)

Always in kilograms, whichever unit the body mass above is given in. Fill it in to see what you would weigh standing there.

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Mass Measured In

Orbit Radius Measured In

A circular orbit at a given radius from the centre of the body being orbited.

Mass of the Central Body (Earth masses) *

Orbit Radius From the Centre (km) *

Measured from the centre of the central body, so add its radius to the altitude.

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