Orbital Period Calculator (Kepler's Third Law)
Calculate the orbital period of any spacecraft from its semi-major axis using Kepler's third law. Supports Earth, Moon, Mars, Sun, and arbitrary central bodies.
What It Does
The Orbital Period Calculator applies Kepler's third law (T = 2π × √(a³/μ)) to compute the orbital period of any spacecraft from its semi-major axis. Enter altitude (for circular orbits) or semi-major axis (for elliptical) and the calculator returns the period in seconds, minutes, hours, and revolutions per day. Built-in central body presets cover Earth, Moon, Mars, Venus, Sun, and Jupiter, with a custom μ field for asteroid and small-body missions.
Key Features
- Computes period from altitude (circular) or semi-major axis (elliptical)
- Output in seconds, minutes, hours, and revolutions per sidereal day
- Central body presets for Earth, Moon, Mars, Venus, Sun, Jupiter
- Custom gravitational parameter input for small bodies and asteroids
Why It Matters
Orbital period drives almost everything downstream of orbit selection: revisit time over a target, ground station contact frequency, eclipse cadence, thermal cycling rate, and battery cycle life. A LEO mission at 400 km has 90-minute periods and 16 revs/day; one at 800 km has 100-minute periods and 14 revs/day. That difference cascades into ConOps, downlink scheduling, and even battery sizing. Getting the period right at concept stage anchors the rest of the mission timeline.
Calculator
T = 2π√(a³/μ)
Inputs
Result
What this does not model. Two-body Keplerian motion. No J2, no drag, no third-body effects. For a circular orbit the altitude is the semi-major axis above the surface; for an elliptical one, enter the semi-major axis altitude.
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Included in every plan
The aerospace pack ships 127 calculators, and there are 478 across all 20 industry packs. Plans start at $14.99/month.