Orbital Speed Calculator
Use this tool to estimate circular orbital velocity for satellites around Earth, the Moon, Mars, Jupiter, the Sun, or a custom celestial body.
v = √(μ / r)Where
μ = G × M (standard gravitational parameter) and r is orbital radius from the center of the body.
What is orbital speed?
Orbital speed is the velocity an object needs to stay in orbit around another object, such as a satellite around Earth. If the speed is too low, gravity pulls the object down. If the speed is too high, it can move to a higher orbit or even escape gravity entirely.
In a perfectly circular orbit, the speed is constant. In an elliptical orbit, speed changes continuously: faster near periapsis (closest point) and slower near apoapsis (farthest point).
The circular orbit equation
This calculator uses the circular-orbit formula:
v = √(μ / r)
- v = orbital speed (m/s)
- μ = standard gravitational parameter of the central body (m³/s²)
- r = distance from the center of the body to the orbiting object (m)
Since users usually know altitude above surface instead of center distance, we compute:
r = body radius + altitude.
How to use this orbital speed calculator
Step-by-step
- Select a central body (Earth, Moon, Mars, Jupiter, Sun, or Custom).
- Enter orbit altitude in kilometers.
- Choose your preferred speed unit.
- Click Calculate Orbital Speed.
The result panel returns:
- Orbital speed in your chosen unit
- Orbital radius from center
- Approximate orbital period
- Local escape speed at that altitude
- Local gravitational acceleration
Worked examples
Example 1: ISS-like low Earth orbit
For Earth at around 400 km altitude, the speed is close to 7.67 km/s (about 27,600 km/h). That is why satellites in low Earth orbit complete a trip around Earth in roughly 90 minutes.
Example 2: Low lunar orbit
Around the Moon at low altitude, orbital speed is much lower than around Earth because lunar gravity is weaker. This has a major effect on mission design, fuel requirements, and insertion burns.
Circular vs elliptical orbit speed
This page calculates circular speed only. Real missions often use elliptical transfer orbits, where speed is computed using the vis-viva equation:
v = √(μ × (2/r - 1/a)), where a is semi-major axis.
If you are planning transfer maneuvers (Hohmann transfer, bi-elliptic transfer, etc.), use this calculator for quick circular checks, then move to a mission-analysis tool for full trajectory planning.
Common mistakes to avoid
- Mixing kilometers and meters in the same equation.
- Entering altitude when the equation expects center-to-center radius.
- Confusing orbital speed with escape velocity.
- Using Earth values for non-Earth bodies without updating gravitational parameters.
FAQ
Is orbital speed the same as escape speed?
No. Circular orbital speed is lower. Escape speed is √2 times circular speed at the same radius.
Why does orbital speed decrease at higher altitude?
As orbital radius increases, gravity is weaker, so less speed is needed to maintain orbit.
Can this calculator be used for planets outside our solar system?
Yes. Use the Custom Body option, enter estimated mass and radius, and the calculator will compute the corresponding circular speed.
Final takeaway
Orbital mechanics looks complex, but the core circular-speed relationship is simple and powerful. With the right gravitational parameter and orbital radius, you can estimate satellite velocity in seconds and build intuition for how missions behave around different worlds.