Escape Energy Calculator

About this calculator

This calculator finds the gravitational escape energy, E = G·M·m/r, the minimum energy an object of mass m needs to break free from a celestial body of mass M and radius r without any further propulsion, derived by setting the object's kinetic energy equal to the gravitational potential energy well it must climb out of. This is directly related to escape velocity, v = √(2GM/r), the speed at which that energy is entirely kinetic.

Aerospace engineers use this to calculate the minimum energy — and therefore fuel — a rocket needs to leave Earth's or another planet's gravity well, mission planners use it when comparing launch requirements from different bodies (the Moon needs far less escape energy than Earth), and astrophysicists use the underlying concept when discussing black holes and gravitational binding energy. Physics students and spaceflight enthusiasts use this calculator to see just how much energy gravity demands before something can leave for good.