Orbital Period Calculator
How long is one lap? Orbit time for any altitude, any world.
Enter an altitude above the surface and instantly see how long one full orbit takes there, for every planet, the Moon, Pluto and the Sun — using the real orbital-mechanics formula behind Kepler's third law (T = 2π√(r³/GM)). Compare the International Space Station's ~93-minute orbit, a 24-hour geostationary orbit, and everything in between. Runs fully in your browser — nothing is uploaded.
About Orbital Period Calculator
- Jump straight to a specific planet with the searchable dropdown.
- Change the altitude once and every world's orbital period recalculates instantly.
- No sign-up, no app — 100% free and private, everything runs in your browser.
Orbital Period Calculator features
- Orbital period for every planet, the Moon, Pluto and the Sun
- The real formula behind Kepler's third law (T = 2π√(r³/GM))
- A plain-language formula walkthrough with a worked example and diagram
- Real NASA photos related to the topic, pulled from NASA's public image archive
- Instantly compares the same altitude across the whole solar system
- Searchable dropdown to jump straight to a specific world
- A short fun fact for every world
- Free, key-less, and 100% client-side — nothing you enter is uploaded
How to use Orbital Period Calculator
Enter an altitude
Type how high above the surface the orbit is, in kilometres — the ISS's real altitude (408 km) is the starting default.
Scan the results
Each card shows the same altitude applied to every planet, moon and the Sun, with the resulting orbital period.
Jump to a world
Use the dropdown to scroll straight to Mars, Jupiter, the Moon or any other body.
See the pattern
Notice how the same altitude gives wildly different times on different worlds — that's just each planet's own gravity at work.
Frequently asked questions
How do you calculate orbital period?
It comes down to two things: how far you are from the planet's centre, and how strong that planet's gravity is. Farther out, or weaker gravity, means a longer orbit. Closer in, or stronger gravity, means a faster one. Want the exact maths? See the "How the formula works" section above — it walks through the real equation step by step with a worked example.
How long does it take to orbit Earth at 400 km altitude?
About 92-93 minutes — this is the International Space Station's real orbit. At that altitude, a spacecraft completes just over 15 orbits of Earth every day.
Why do geostationary satellites take exactly 24 hours?
Because engineers deliberately place them at the one height (about 35,786 km above the equator) where the orbit naturally takes the same time as Earth's own spin — about 24 hours. So the satellite seems to "hang" motionless over the same spot on the ground, which is exactly what's needed for TV and weather satellites.
Does a heavier satellite orbit slower?
No. Orbital period depends only on the altitude and the planet's gravity — not on the orbiting object's mass. A pebble and a fully loaded space station released at the same altitude complete their orbit in exactly the same time.
How long is one orbit around the Moon?
At a low altitude (around 100 km, similar to Apollo's Command Module), one orbit of the Moon takes roughly 2 hours — faster than you might expect, because low lunar orbits sit very close to the Moon's centre relative to its small size.
What is "mu" (μ) or GM in the formula?
It's just one number that tells you how strongly a planet pulls things toward it — a bigger number means a stronger pull. You don't need to know the planet's mass in kilograms yourself; this calculator already has that number ready for every world in the solar system.
Is this orbital period calculator free?
Yes — completely free, with no sign-up and no app to install. Every calculation runs instantly in your browser, and nothing you enter is stored or uploaded.
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