Planetary Escape Velocity Calculator
Escape velocity is the speed at which an object launched from a body's surface has just enough kinetic energy to climb out of that body's gravity well forever. It depends only on the body's mass and radius, not on what is escaping, because the escaping object's mass cancels from the energy balance. From the gentle pull of a small moon to the crushing grip of a star, the same square-root formula applies. This calculator takes a body's mass and radius and returns the escape velocity in both meters and kilometers per second.
Escape velocity formula
v_escape = sqrt(2 * G * M / r)
km/s = v_escape / 1000
surface gravity g = G * M / r^2
The formula comes from equating the kinetic energy of the launched object to the gravitational potential energy needed to reach infinity. The escaping object's own mass cancels, so escape velocity depends only on the body's mass and radius. Surface gravity is shown for context.
Escape velocity facts
- Earth's escape velocity is about 11.2 kilometers per second.
- The Moon's is about 2.4 kilometers per second, too low to hold a thick atmosphere.
- Jupiter's is roughly 59.5 kilometers per second, the highest of the planets.
- Escape velocity is independent of the mass of the escaping object.
- The defaults model Earth using its standard mass and mean radius.
Escape velocity: frequently asked questions
What is escape velocity?
Escape velocity is the minimum speed an object needs at a body's surface to break free of its gravity and never fall back, ignoring atmospheric drag and any further propulsion. At exactly escape velocity, the object's kinetic energy equals the gravitational binding energy, so it coasts to infinity with zero speed remaining.
What is the escape velocity formula?
v_escape = sqrt(2 G M / r), where G is the gravitational constant, M is the body's mass, and r is the distance from its center (the surface radius for surface escape velocity). The speed grows with the square root of mass and falls with the square root of radius.
What is Earth's escape velocity?
Using Earth's mass of about 5.972e24 kg and radius of about 6.371e6 m, the formula gives roughly 11,186 meters per second, or about 11.2 kilometers per second. The Moon's much lower mass gives only about 2.4 kilometers per second, which is why it could not retain a thick atmosphere.
Does escape velocity depend on the escaping object's mass?
No. The mass of the escaping object cancels out of the energy balance, so a pebble and a spacecraft need the same escape speed from the same body. What differs is the energy required, which does scale with the object's mass, but the threshold speed itself does not.
What units does this calculator use?
Enter the body's mass in kilograms and its radius in meters; the gravitational constant is a user-editable input preset to the 2022 CODATA value 6.674e-11 N m^2 / kg^2. The escape velocity is returned in meters per second and converted to kilometers per second for convenience.
Official sources
- NASA: Planetary fact sheet.
- NIST: CODATA Newtonian constant of gravitation.
Reviewed by the CalculatorHub team, edited by James Graham, 16 June 2026. See our methodology.