Orbital Velocity Calculator
How fast a satellite must travel to stay in a circular orbit at a given altitude — around Earth, the Moon, Mars, the Sun or any mass you enter — with the period and the escape speed at that height.
In a circular orbit gravity supplies exactly the centripetal force: v = √(GM ÷ r), where r is the distance from the centre of the body, not the altitude.
How the orbital velocity calculator works
In a circular orbit gravity supplies exactly the centripetal force: v = √(GM ÷ r), where r is the distance from the centre of the body, not the altitude. Lower orbits are faster — 7.7 km/s at 400 km around Earth, 3.1 km/s at geostationary height — and the period follows from the circumference. Escape speed at the same radius is √2 times the orbital speed.
Formula: v = √(GM ÷ r); T = 2πr ÷ v; v_escape = √2 × v
Worked examples
| Inputs | Orbital velocity | Note |
|---|---|---|
| Earth, 400 km (ISS) | 7.672 km/s | 7.67 km/s, 92.6 min |
| Geostationary, 35,786 km | 3.075 km/s | 3.07 km/s, 23.9 h |
| Low lunar orbit, 100 km | 1.633 km/s | 1.63 km/s |
FAQFrequently asked questions
Why is a lower orbit faster?
Gravity is stronger closer in, so a satellite must move faster for its curvature to match the pull. The trade-off is that it takes more energy per kilogram to reach a higher orbit even though the speed there is lower.
What altitude do common satellites use?
The ISS about 400 km (7.67 km/s, 92 minutes); Starlink 550 km; GPS 20,200 km (3.9 km/s, 12 hours); geostationary 35,786 km (3.07 km/s, 24 hours), where the satellite hangs over one spot.
Does the mass of the satellite matter?
No — the speed depends only on the central mass and the distance. A pebble and a space station at the same altitude orbit at the same speed.
What about elliptical orbits?
Speed varies along an ellipse — fastest at periapsis, slowest at apoapsis — following the vis-viva equation. The circular figure here is the speed at that radius for a circular path; the Hohmann transfer calculator handles the ellipse between two.
Where these figures come from
- NIST — CODATA 2018 fundamental physical constants — G and the speed of light
- IAU 2015 Resolution B3 — nominal solar and planetary conversion constants — the astronomical unit, solar mass and planetary radii
- Royal Observatory Greenwich — the historic home of the prime meridian
Last checked: September 2026. Constants are CODATA 2018 (G, c) and IAU 2015 nominal values (solar and planetary parameters).