What Is a Circular Orbital Velocity Calculator?
This calculator finds the exact speed an object needs to maintain a stable circular orbit around a central body, using Newton's law of gravitation. Give it the central body's mass and the orbital radius (measured from the body's center), and it returns the required orbital velocity, the time for one full orbit, and the escape velocity at that same distance.
This is the same core relationship mission planners use to work out how fast a satellite must travel to stay in orbit instead of falling back to the surface or drifting away into space.
How to Read Your Results
Orbital Velocity
This is the speed, in kilometers per second, needed to keep a circular orbit at your chosen radius. Fly slower and gravity wins, pulling the object into a lower, decaying path; fly faster and it will climb into a higher orbit instead.
Velocity (mph)
The same orbital speed converted to miles per hour, which is often easier to picture — low Earth orbit speeds are typically around 17,000 mph.
Orbital Period
How long one complete trip around the central body takes at this radius and speed, calculated from the orbit's circumference divided by the orbital velocity.
Escape Velocity at This Radius
The speed needed to break free of the central body's gravity entirely from this distance. It is always exactly √2 (about 1.414) times the circular orbital velocity.
Real-World Example
The International Space Station orbits Earth at an altitude of roughly 400 km, which is about 6,771 km from Earth's center.
| Quantity | Result |
|---|---|
| Central body mass | 5.972 × 10²⁴ kg (Earth) |
| Orbital radius | 6,771 km |
| Orbital velocity | ≈7.67 km/s (≈17,150 mph) |
| Orbital period | ≈92 minutes |
These numbers line up closely with the ISS's real orbital speed of about 7.66 km/s and period of about 92.7 minutes, confirming the formula matches real spaceflight data.
Tips for Using This Calculator
- Always measure radius from the center of the body, not the surface — add the body's radius to any altitude above ground.
- Lower orbits are faster but decay sooner due to atmospheric drag near a planet.
- Higher orbits are slower and take longer to complete, which is why geostationary satellites sit much farther out than the ISS.
- Use the Custom option to model orbits around moons, asteroids or exoplanets by entering their known mass.
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Last updated: August 2026 · Reviewed by: Simple Calculator Tools Editorial Team