Orbital Velocity Calculator
Find the speed needed to orbit a body.
Results update as you type.
How it works
Orbital velocity is the speed an object must travel to stay in a stable circular orbit, and this calculator computes it. You enter the mass of the central body being orbited and the orbital radius, the distance from the center of that body, and it returns the orbital velocity in meters and kilometers per second along with the orbital period. The formula comes from setting gravity equal to the centripetal force required for circular motion, which yields a velocity equal to the square root of the gravitational constant times the central mass divided by the radius. This shows two key relationships: orbiting a more massive body requires a higher speed, and orbiting at a larger radius requires a lower speed, which is why distant planets move more slowly than close ones. For a satellite in low Earth orbit, the velocity is about 7.8 kilometers per second, while the Earth orbits the Sun at roughly 29.8 kilometers per second. The orbital period, the time for one complete revolution, follows directly as the circumference divided by the velocity. These calculations are essential for satellite deployment, mission planning, and understanding planetary motion. Note the radius is measured from the center of the central body, so for a satellite you add the body's radius to its altitude. Both the mass and radius must be positive. Enter the central mass and orbital radius to find the orbital velocity and period.
v = √(G·M / r)
For a circular orbit, gravity provides exactly the centripetal force needed, so the orbital velocity is the square root of the gravitational constant times the central mass divided by the orbital radius. The period follows as the orbit's circumference divided by that speed. Larger masses require higher speeds; larger radii require lower speeds.
Source:Orbital mechanics
We review all our tools from time to time to ensure accuracy.
Worked example
How to use this calculator
- 1
Enter your values
Enter central body mass and orbital radius.
- 2
Adjust the options
Fine-tune any options to match your situation.
- 3
Read your result
Orbital velocity updates instantly as you type — no button to press.
Frequently asked questions
What is orbital velocity?
Orbital velocity is the speed an object needs to maintain a stable circular orbit around a central body. At this speed, the body's gravity provides exactly the centripetal force required to keep the object curving around it rather than flying off or falling in. It depends on the central mass and the orbital radius.
How is orbital velocity calculated?
It equals the square root of the gravitational constant times the mass of the central body divided by the orbital radius. This comes from equating gravitational force with the centripetal force needed for circular motion. The calculator applies this formula and also computes the orbital period from the velocity and the orbit's circumference.
Why do higher orbits have lower speeds?
Because orbital velocity is inversely related to the square root of the radius, a larger orbit means a slower speed. Farther from the central body, gravity is weaker, so less speed is needed to balance it. This is why low satellites orbit faster than high ones, and inner planets orbit the Sun faster than outer planets.
Is the radius measured from the surface or the center?
The orbital radius is measured from the center of the central body, not its surface. So for a satellite orbiting Earth, you add Earth's radius, about 6,371 kilometers, to the satellite's altitude to get the orbital radius. Using altitude alone would give an incorrect, too-small radius and an inaccurate velocity.
How is the orbital period found?
The orbital period, the time for one full revolution, equals the circumference of the orbit divided by the orbital velocity. Since the circumference is two pi times the radius, the period grows with larger orbits both because the path is longer and the speed is lower. The calculator reports the period in seconds.