Planet Orbital Speed Calculator
Planets closer to the Sun feel a stronger pull and must race around faster to stay in orbit, which is why Mercury sprints while Neptune crawls. For a near circular orbit the speed equals the square root of the Sun gravitational parameter divided by the orbit radius, a clean result from balancing gravity against the centripetal need. This calculator takes an orbital radius in astronomical units and returns the average orbital speed in kilometers per second and miles per hour, along with the full orbit circumference. Preset buttons load the real distances of the planets. Use it to compare how the solar system slows down with distance. Everything is computed locally in your browser.
How to use Planet Orbital Speed Calculator
- Enter the orbital radius from the Sun.
- Read the circular orbital speed in kilometers per second.
- Note the equivalent speed in miles per hour where shown.
Frequently asked questions
How does it work out a planet orbital speed?
For a near-circular orbit it uses the vis-viva circular speed, the square root of G times the Sun mass over the orbit radius, giving speed in km/s and mph.
Why do inner planets move faster?
Circular speed falls as orbit radius grows, so Mercury near the Sun races at about 47 km/s while distant Neptune crawls at around 5 km/s.
Is this the same as orbital velocity?
For a circular orbit yes; it is the steady tangential speed the planet keeps, though real orbits are slightly elliptical so speed varies a little through the year.
What is Planet Orbital Speed Calculator?
Planets closer to the Sun feel a stronger pull and must race around faster to stay in orbit, which is why Mercury sprints while Neptune crawls. For a near circular orbit the speed equals the square root of the Sun gravitational parameter divided by the orbit radius, a clean result from balancing gravity against the centripetal need.
Is Planet Orbital Speed Calculator free to use?
Yes. Planet Orbital Speed Calculator is completely free, with no sign-up and no usage limits.
Does Planet Orbital Speed Calculator work in a web browser?
Yes. Planet Orbital Speed Calculator runs in any modern web browser. There is nothing to download or install.
Is my data private with Planet Orbital Speed Calculator?
Yes. Planet Orbital Speed Calculator runs entirely on your device in your browser, so nothing you enter is uploaded to a server.
Badge
Link this tool from a README, doc or site. The badge links back to this page.
[](https://yourhack.ai/planet-orbital-speed-calculator)