Orbital Velocity Calculator (Circular Orbit Speed and Period)
Choose a body and enter the orbit altitude.
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Orbital Velocity Calculator (Circular Orbit Speed and Period) by TheCalcTools
How the Orbital Velocity Calculator (Circular Orbit Speed and Period) works
In a circular orbit gravity provides exactly the centripetal force: v = √(GM ÷ r), where r is measured from the body’s centre. The period is 2π√(r³ ÷ GM) and escape speed is √2 times the orbital speed.
GM values: Earth 3.986004418 × 10¹⁴, Moon 4.9048695 × 10¹², Mars 4.282837 × 10¹³ and Sun 1.32712440018 × 10²⁰ m³/s², with mean radii.
The formula
Worked example
Using the default values shown in the calculator:
| Central body | Earth |
|---|---|
| Altitude above the surface (km) | 400 |
- At 400 km above Earth: 7.673 km/s, one orbit every 92.4 minutes.
Result:
| Orbital speed (km/s) | 7.673 |
|---|---|
| In km/h | 27,621 |
| Orbital period (minutes) | 92.4 |
| Escape velocity at this altitude (km/s) | 10.851 |
Frequently asked questions
How fast does the ISS go?
At about 400 km it orbits at roughly 7.67 km/s, once every 92 to 93 minutes.
Sources and further reading
- Wikipedia: Orbital speed
- Wikipedia: Standard gravitational parameter
- NASA NSSDC: Planetary Fact Sheet
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