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.
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.
Yes. Planet Orbital Speed Calculator is completely free, with no sign-up and no usage limits.
Yes. Planet Orbital Speed Calculator runs in any modern web browser. There is nothing to download or install.
Yes. Planet Orbital Speed Calculator runs entirely on your device in your browser, so nothing you enter is uploaded to a server.