Calculate orbital period from semi-major axis using Kepler’s third law.
Kepler’s third law states that the square of the period is proportional to the cube of the semi-major axis. That relationship fixes the geostationary radius at about 42,164 km for Earth. The cube-root dependence means large changes in altitude produce modest changes in period, which is why geostationary orbit sits so far out.
Orbital Period
T = 2π √(a³ ÷ GM)
T = 2π √(a³ ÷ GM) Kepler’s third law states that the square of the period is proportional to the cube of the semi-major axis. That relationship fixes the geostationary radius at about 42,164 km for Earth.
The cube-root dependence means large changes in altitude produce modest changes in period, which is why geostationary orbit sits so far out.
This calculator takes 2 inputs: Mass of the central body, Semi-major axis. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.