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Calculate the minimum escape velocity from any celestial body's surface, with support for custom celestial parameters.
Overview
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Escape speed is the ideal minimum speed at a stated distance from a body’s center for an object to escape that body’s gravity without continued propulsion, in a simplified Newtonian model. For a spherical body, the surface estimate is v = √(2GM/r), where G is the gravitational constant, M is body mass, and r is the center-to-surface radius. NASA’s gravity reference gives this relation; NASA/JPL orbital-mechanics material treats escape as a trajectory condition rather than a practical launch-speed prescription. NASA Goddard: gravity questions · NASA/JPL: orbital mechanics, chapter 7.
The calculator also reports surface gravity from g = GM/r². Presets are available for Earth, Moon, Mars, Jupiter, and Sun, or you can enter a custom mass and radius.
Guide
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Select a preset body, or switch to custom input.
For a custom estimate, enter mass in kilograms and radius in meters. Use positive values for the same body; scientific notation such as 5.972e24 is suitable for large masses.
Read escape speed in meters per second and kilometers per second, plus the calculated surface gravity and the parameter values used.
As a check, Earth’s preset (5.972 × 10²⁴ kg and 6.371 × 10⁶ m) gives about 11.18 km/s from the displayed formula. The calculation uses the preset values; small differences from other references can follow from the chosen constants and rounded body parameters.
Use cases
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Because speed scales with the square root of mass divided by radius, increasing mass raises the estimate and increasing radius lowers it, all else equal.
Q&A
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No. This is an idealized escape-speed calculation. An actual launch depends on propulsion over time, atmosphere, rotation, launch direction, trajectory, and other gravitational bodies. It is not a mission design or launch-planning result.
The preset reports surface values. In custom mode, the formula uses distance from the body’s center; for an estimate at altitude, use the body’s radius plus that altitude, both in meters.
They are the same speed in different units: 1 km/s equals 1,000 m/s. The calculator reports both alongside surface gravity.
Notes
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This is a Newtonian, isolated-body estimate based on the entered mass and center-to-surface distance. It does not account for atmospheric drag, rotation, other bodies, or continued thrust. A matching value does not determine whether a real vehicle or object can follow a particular escape trajectory. Use appropriate scientific or mission-analysis methods for engineering decisions.
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