Circular Orbit Velocity Calculator

The exact speed that keeps an orbit stable

A circular orbit requires a very specific speed at a given radius - fast enough that gravity cannot pull the object all the way down, but not so fast that it escapes entirely. This balance point is the circular orbital velocity.

Worked example

For a satellite at a 6,780 km orbital radius around Earth (mu = 398,600 km3/s2), close to the International Space Station's actual orbit:

v(circular) = sqrt(398600 / 6780) = 7.6675 km/s

Frequently asked questions

How does this compare to escape velocity? Escape velocity at any given radius is always exactly sqrt(2) times the circular orbital velocity at that same radius - so a satellite would need to speed up by about 41% from stable orbit to break free of Earth's gravity entirely.

Does this match the ISS's real speed? Yes - the International Space Station orbits at roughly this radius and travels at approximately 7.66 km/s, matching this calculation closely, which is what allows it to complete a full orbit in about 92-93 minutes.