Orbital Period Calculator
Calculate the time to complete one orbit using Kepler's third law.
This tool is for informational and educational purposes only. It is not a substitute for professional financial, medical, legal, or engineering advice. See Terms of Service.
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Request a ToolHow to Use the Orbital Period Calculator
Enter the central body mass and the semi-major axis of the orbit. The calculator returns the orbital period in seconds, hours, and days.
- Enter central mass. For Earth, use 5.972 x 10^24 kg. For the Sun, use 1.989 x 10^30 kg.
- Enter semi-major axis. This is the average orbital distance from the center of the body.
- Read the result. The period appears in seconds with conversions to hours and days.
About the Orbital Period Calculator
Kepler's third law states that the square of the orbital period is proportional to the cube of the semi-major axis. The formula T = 2*pi*sqrt(a^3/(GM)) lets you calculate how long it takes any satellite or planet to complete one orbit. The ISS completes one orbit in about 92 minutes. The Moon takes 27.3 days. Earth takes 365.25 days to orbit the Sun. This law applies to any two-body gravitational system.
Frequently Asked Questions
How long does it take the ISS to orbit Earth?
The ISS completes one orbit approximately every 92 minutes (about 5,560 seconds) at an altitude of roughly 400 km.
Does the orbiting object's mass affect the period?
For practical purposes, no. The formula assumes the orbiting mass is much smaller than the central body. For comparable masses (like binary stars), a modified form is used.
What is a geosynchronous orbit period?
A geosynchronous orbit has a period of exactly 23 hours, 56 minutes, and 4 seconds (one sidereal day), at an altitude of approximately 35,786 km above Earth.