Kepler Third Law Calculator

P^2 = a^3 (in AU and years for solar orbits)

Semi-Major Axis (AU)

Central Star Mass (Solar Masses)

Orbital Period (years)

Central Star Mass (Solar Masses)

Formula

P^2 = a^3 / M (years, AU, solar masses)

What is Kepler third law?

P^2 = a^3/M. The square of the period is proportional to the cube of the semi-major axis, divided by the central mass.

Does this work for all orbits?

Yes, it applies to any two-body gravitational system: planets, moons, binary stars, etc.

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