# Calculate Orbital Speed

Calculator for the orbital speed, the velocity of a celestial body (planet or moon) around another one (star or planet). Celestial bodies have large masses, which are often measured in Earth, Jupiter or Solar masses. You can also select kilograms. The total mass is the mass of both bodies together. For the radius, the common unit is AU, astronomical unit, which is the average distance of the Earth from the Sun. Here you can also choose meters, kilometers or miles. For the velocity, there are meters, kilometers and miles, per hour or per second. Please enter two values and select the units. The third value will be calculated.

The formula is:

velocity = √ gravitational constant * total mass / orbit radius

v = √ G * M / r

Gravitational constant G = 6.6743 * 10^{-11} m³/(kg*s²) = 0.000000000066743 m³/(kg*s²)

Example: Sun has about 332890 times the mass of Earth. So the system Earth-Sun has about one solar mass. At an average radius of one astronomical unit, the average orbital speed is almost 30 kilometers per second.

German: g-Beschleunigung