Escape Velocity Calculator
Escape velocity is the speed an object needs to get far enough from a body that the body's gravity can no longer pull it back. This ignores air and any thrust applied after launch.
- Free
- Works offline after your first visit
- Saves on this device
- No sign-up
- Updated
How it works
Escape velocity is the square root of two times the gravitational constant times the body's mass, divided by the radius. The gravitational constant is about 6.674 times ten to the minus eleven in SI units.
Enter the radius from the centre of the body. The choice sets the mass, so enter the radius that matches the body you picked. Air drag and the launch path change what a real launch needs.
Worked example
From a body with the mass you picked and a radius of 3,959 mi, the escape speed is about 25,021 mph.
Questions
Does a rocket need this speed to leave Earth?
Not in practice. A rocket climbs under power and does not have to reach escape speed at the surface. This is the speed for a launch with no further push.
Why does the mass matter?
More mass pulls harder, so an object has to move faster to get away from it.
Does the direction of launch change the number?
Not for a body with no air and no other nearby pull. The direction you throw the object in does not change the figure.
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