Escape Velocity & Orbit Calculator
Find the escape velocity, orbital speed, and orbital period for any planet or moon, at the surface or at any altitude. Pick a body or enter your own mass and radius.
Mass accepts scientific notation, e.g. 5.972e24. Try an altitude of 420 km for the International Space Station's orbit.
How it works
What is escape velocity?
The minimum speed an object needs to coast away from a planet's gravity forever, without any more thrust and ignoring air resistance. From Earth's surface it's about 11.2 km/s (roughly 25,000 mph).
How is it different from orbital velocity?
Orbital velocity is the speed needed to circle the planet at a given height without falling back. Escape velocity is always √2 (about 1.414) times the circular orbital velocity at the same distance.
Why does it get smaller with altitude?
Gravity weakens with distance, so the farther from the planet's center you start, the less speed you need. r in the formulas is the distance from the center: the planet's radius plus your altitude.
Where does the data come from?
Masses and mean radii are from NASA's planetary fact sheets, with G = 6.6743 × 10⁻¹¹ N·m²/kg². Results are for idealized spheres with no atmosphere or rotation.