FSpaceRPG article

Status: Official

For worldbuilders or starship pilots, it is important to know the orbital period of a planet around it’s star, a moon around a planet, or a starship in orbit of a planet.

This tool will caluclate the orbital period of one body around another based on Kepler’s 3rd law. This doesn’t take into account relativity - especially in intense gravitational fields and orbital velocities - so orbiting a black hole can’t be reliable calculated with this tool.

Orbits aren’t typically circular - given the central body is often offset by orbiting body gravity, and planets often orbit in elipses around their primary bodies. A semimajor axis is half of the length of the major axis of the orbit which is the longest line from one edge of the elipse to the other (I’ll add a picture later).

For simple gmaing purposes, you can treat orbits as circular and treat the semimajor axis as the orbital distance of the planet from the star (center of each body - not distances between surfaces).

Semimajor axis
Mass of sun
Mass of planet

Orbital period

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