How the Orbital Velocity Calculator works
Circular orbital speed is set by gravity and orbital radius. Around the same body, a lower circular orbit is faster than a higher one. The core relationship used here is For an ideal circular orbit, v = √(μ / r), where r is distance from the central body’s centre. If you are building a complete observing or imaging setup, use the Orbital Period Calculator alongside this page rather than treating one number in isolation.
Worked example and interpretation
At roughly 6770 km from Earth’s centre, a low Earth orbit has an ideal circular speed around 7.7 km/s.
For broader physical context, the NASA/JPL Solar System Dynamics is a useful external reference.
When this calculator is useful
Use it to compare low Earth orbit, geostationary scale and circular orbit speeds around Earth, the Sun or Jupiter.
When the result involves angular size, field, observing conditions or a current target, continue with Escape Velocity Calculator. For a different but related perspective, ISS Tracker can connect the formula to an actual observing, telescope or Solar System context.
Diagrams
Assumptions, accuracy and practical limits
Elliptical orbits change speed continuously and require the vis-viva equation. Drag, thrust and third-body perturbations are outside this simple result.
A second external cross-check is available from NASA Solar System. Not for operational or published work.
Reference table: circular orbital speeds around Earth
| Orbit | Radius | Speed | Speed (km/h) |
|---|---|---|---|
| International Space Station (≈400 km) | 6,771 km | 7.673 km/s | 27,621 km/h |
| Sun-synchronous (≈800 km) | 7,171 km | 7.456 km/s | 26,840 km/h |
| GPS | 26,560 km | 3.874 km/s | 13,946 km/h |
| Geosynchronous | 42,164 km | 3.075 km/s | 11,069 km/h |
| Moon | 384,400 km | 1.018 km/s | 3,666 km/h |
Higher orbits are slower: a geostationary satellite moves at about 3.07 km/s, less than half the ISS speed, yet it needs far more energy to reach because of the climb.
Related SpaceTracker.live tools
Continue with Orbital Period Calculator, Escape Velocity Calculator and ISS Tracker.
Worked scenarios: what the speed means on the ground
A satellite at 400 km altitude moves at 7.67 km/s relative to Earth’s centre. Its sub-satellite point slides over the surface at about 7.22 km/s, so it would cross a 4,500 km continent in roughly 10 minutes.
The speed drops with distance as 1/√r. A GPS satellite at 26,560 km moves at 3.87 km/s and a geostationary one at 42,164 km at 3.07 km/s, about 40% of the ISS-height speed.
Common mistakes and speed lookup
- Measuring from the surface. The radius used is from Earth’s centre, so add 6,371 km to the altitude.
- Forgetting direction. Orbital velocity is the tangential speed; a spacecraft that is merely falling does not orbit.
- Using one speed for an ellipse. The speed changes along an elliptical orbit, fastest at the closest point.
| Altitude | Speed |
|---|---|
| 400 km | 7.67 km/s |
| 550 km | 7.59 km/s |
| 800 km | 7.46 km/s |
| 1,200 km | 7.26 km/s |
| 20,200 km | 3.87 km/s |
| 35,786 km | 3.07 km/s |
More questions answered
Why is the ISS so fast?
At 400 km you need about 7.7 km/s to keep falling around Earth without hitting it; that is the speed at which the curve of the fall matches the curve of the planet.
Does a higher satellite need more speed?
No: the orbital speed is lower at greater distance, but it takes more energy to reach.
Frequently asked questions
Why do higher satellites move more slowly?
Gravity is weaker at greater radius, so less speed is needed to stay on a circular path.
What about elliptical orbits?
Speed varies along the path. This tool gives the circular-orbit value; the vis-viva equation covers elliptical cases.
Is this the speed relative to the ground?
No, it is the speed relative to the planet’s centre, in an inertial frame.