Weight on Other Planets Calculator – Mass, Gravity and W = mg
The Weight on Other Planets Calculator takes a mass or a weight measured on one world and reports what it would weigh on another. Pick any of the eight planets, the Sun, the Moon, dwarf planets such as Pluto, Ceres, Eris and Makemake, the big moons of Jupiter and Saturn, a handful of known exoplanets, or invent a world of your own from its mass and radius. Alongside the headline force you get the surface gravity used, the reading an Earth-calibrated scale would show, and the human consequences: how high you could jump, how long you would hang in the air, and how much you could lift.
Why Weight Changes but Mass Does Not
Mass is the amount of matter in an object and the resistance it offers to being accelerated. It is the same on Earth, on Mars and in deep space. Weight is a force — the pull a gravitational field exerts on that mass — and it changes with wherever you happen to be standing:
W = m · g weight from mass and local gravity
m = W / g the invariant mass behind a weight reading
W₂ = W₁ · (g₂/g₁) moving a weight from one body to another
g = GM / r² surface gravity from mass and mean radius
g(h) = GM / (r+h)² gravity at height h above the surfaceA 70 kg person is 70 kg everywhere. On Earth that is a weight of about 687 N; on Mars, where g ≈ 3.73 m/s², it is only 261 N. A bathroom scale taken to Mars would read about 26.6 kg — not because you lost anything, but because the scale measures force and is marked in mass units assuming Earth gravity.
Why Big Planets Are Not Always Heavy Underfoot
Surface gravity divides mass by the square of the radius, which produces results most people find counter-intuitive. Saturn carries 95 Earth masses, yet its one-bar level sits more than nine Earth radii from the centre, so its surface gravity is barely above our own. Uranus, with 14 Earth masses, comes out at roughly 0.9 g — you would weigh lessthere than at home. Meanwhile a small dense world can bite hard: the calculator's custom mode lets you build a super-Earth of 5 M⊕ and 1.6 R⊕ and watch it land near 1.95 g, enough to make climbing a staircase a workout.
Altitude, Orbit and the Free-Fall Myth
Enter an altitude and the tool switches to g(h) = GM/(r+h)². At the International Space Station's 400 km, Earth's field is still about 89% of its surface value. Astronauts float because the station, the astronaut and the coffee cup are all falling around the planet together, not because gravity has vanished. The altitude chart makes the point visually: to halve your weight you would have to climb to about 2,600 km, and geostationary orbit still leaves you with a little over 2% of surface gravity.
Rotation, Latitude and Real Scales
Spin subtracts a small centrifugal term, g_eff = g − ω²·r·cos²(latitude). On Earth this is why the same scale reads roughly 0.35% lighter at the equator than at the poles — a genuine effect that athletics record keepers and precision metrologists care about. Switch the correction on and set a latitude to see it. For fast rotators the term is far from small, which is part of why Haumea, spinning once every four hours, is shaped like an egg rather than a ball.
What Low Gravity Would Feel Like
Because a jump converts a fixed amount of leg energy into height, h ∝ 1/g. Your 0.5 m Earth jump becomes roughly 3 m on the Moon and about 1.3 m on Mars, with hang time stretching from 0.6 s to nearly 4 s. Falling slows down as well — a 1 metre drop takes 0.45 s on Earth and 1.1 s on the Moon, which is exactly why Apollo crews looked as though they were filmed in slow motion. The same ratio applies to lifting: a 100 kg Earth deadlift becomes roughly 600 kg of Moon rock, though your muscles still have to deal with all that inertia when you try to stop it moving.
Where the Numbers Come From
Every body's mass and mean radius is taken from the published NASA planetary fact sheets, and each surface gravity shown here is derived from those two figures rather than typed in separately, so the values stay internally consistent and reproduce the standard published numbers to within a few tenths of a percent. Two caveats are worth keeping in mind. For the Sun and the giant planets there is no surface to stand on; the quoted level is the photosphere or the one-bar pressure altitude. And real local gravity varies with terrain, density anomalies and latitude, so treat any single figure as the global average it is.