Orbital Velocity Calculator
Find the speed a satellite needs to stay in a circular orbit around any central body from its mass and orbital radius.
How it works
v = √(G·M ÷ r) · G = 6.674×10⁻¹¹ N·m²/kg²
For a circular orbit the inward gravitational pull must exactly supply the centripetal force, which sets a single speed at every radius: v = √(GM/r). It depends only on the central mass and the orbital radius, not on the satellite’s own mass. Orbit lower and you must fly faster; orbit higher and the required speed falls off with the square root of distance.
Worked example
For a satellite 400 km above Earth (radius r = 6,371 + 400 = 6,771 km = 6.771×10⁶ m) around Earth’s mass 5.972×10²⁴ kg: v = √(6.674×10⁻¹¹ × 5.972×10²⁴ ÷ 6.771×10⁶) ≈ 7,673 m/s, about 7.67 km/s.
Sources: Orbital speed — Wikipedia
Frequently asked questions
Does a heavier satellite need to go faster?
No. The satellite’s mass cancels out of the equation, so a bolt and a space station at the same altitude orbit at the same speed. Only the central body’s mass and the orbital radius matter.
Why do low orbits move faster than high ones?
Gravity is stronger closer in, so more centripetal force is available and the balancing speed is higher. The International Space Station in low orbit races along at ~7.7 km/s, while a geostationary satellite far out cruises at only ~3.1 km/s.
Is this the same as escape velocity?
No — escape velocity is √2 (about 1.414) times the circular orbital velocity at the same radius. Reaching escape speed lets an object leave for good rather than circle.
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This calculator is for educational purposes. Double-check important results before acting on them.