Orbital Velocity Calculator
The orbital velocity calculator computes the speed, orbital period, and other parameters for circular orbits around Earth or any massive body. Orbital mechanics, derived from Newton's law of universal gravitation, determines the altitudes and speeds of satellites, the International Space Station, the Moon, and planetary bodies. Understanding orbital velocity is fundamental to space mission design, satellite constellation planning, and understanding how gravity shapes the universe. Enter the orbital altitude above Earth's surface (or specify any central body mass and radius) to calculate the orbital velocity, period, and escape velocity.
Orbital mechanics formulas
Orbital velocity: v = sqrt(G*M / r)
Orbital period: T = 2*pi*r / v = 2*pi*sqrt(r^3 / (G*M))
Escape velocity: v_esc = sqrt(2*G*M / r) = v * sqrt(2)
G = 6.674e-11 N*m^2/kg^2
r = body_radius + altitude
Notable Earth orbits
- Low Earth Orbit (LEO): 160 to 2,000 km, period 88 to 127 min, v ~7.8 km/s.
- ISS: ~408 km, period ~92.7 min, v ~7.66 km/s.
- Medium Earth Orbit (MEO): 2,000 to 35,786 km (GPS at ~20,200 km).
- Geostationary (GEO): 35,786 km, period 24 h, v ~3.07 km/s.
Orbital velocity: frequently asked questions
What is orbital velocity?
Orbital velocity is the speed a satellite must maintain to stay in a circular orbit at a given altitude. Gravity provides the centripetal force: v = sqrt(G*M/r), where G = 6.674e-11 N*m^2/kg^2, M is the central body mass, and r is the orbital radius (distance from center of the central body). For Earth (M = 5.972e24 kg, R_E = 6,371 km), a satellite 400 km above the surface orbits at about 7.66 km/s.
What is the International Space Station orbit?
The ISS orbits at approximately 408 km altitude (r = 6,779 km from Earth's center), with an orbital velocity of about 7.66 km/s and an orbital period of about 92.7 minutes (nearly 16 orbits per day). The ISS experiences a small atmospheric drag that causes gradual orbital decay, which is corrected by periodic reboost maneuvers.
What is escape velocity vs orbital velocity?
Escape velocity = sqrt(2) * orbital velocity at the same radius. At Earth's surface: orbital velocity = 7.91 km/s; escape velocity = 11.19 km/s. To escape Earth's gravity entirely (without returning), a spacecraft must exceed escape velocity. A satellite in orbit is effectively in continuous free fall: it falls toward Earth but its horizontal velocity carries it over the horizon.
What is geostationary orbit?
Geostationary orbit (GEO) is a circular equatorial orbit where the satellite completes one orbit in exactly 24 hours (one sidereal day = 23h 56m 4s), remaining stationary over a fixed point on the equator. The altitude is approximately 35,786 km above Earth's surface (r = 42,164 km from center). Orbital velocity at GEO is about 3.07 km/s.
How does orbital velocity change with altitude?
Orbital velocity decreases with altitude: v = sqrt(G*M/r). Doubling the orbital radius reduces v by a factor of sqrt(2) (about 29%). Higher orbits are slower. This is counterintuitive but follows from Kepler's laws: inner planets/satellites travel faster. The orbital period increases as r^(3/2) (Kepler's third law): T = 2*pi*r/v = 2*pi*sqrt(r^3/(G*M)).
Official sources
Reviewed by the CalculatorHub team, edited by James Graham, 14 June 2026. See our methodology.