What the same body would weigh across the solar system, from Pluto to the Sun.
Here's the one that catches people out: you would weigh slightly less on Saturn than you do on Earth. It has ninety-five times our mass, but it is so enormously spread out — less dense than water — that the pull at its cloud tops comes to about 0.92 of Earth's. Everything else on this page is more or less what you'd expect. Saturn isn't.
Bars are scaled against Earth's gravity. The Sun's runs off the end of the scale — at nearly twenty-eight times Earth's pull, it wouldn't fit.
How it works
The sum itself is the easy part. Weight is the force gravity exerts on a mass:
weight = mass × surface gravity
Since your mass is the same wherever you go, comparing two places only needs the ratio of their gravities. Each body's surface gravity is given here as a multiple of Earth's, so:
weight there = weight on Earth × gravity factor
A body's surface gravity comes from its mass and its radius together — specifically GM / r². That is why size alone tells you very little. Mercury is much smaller than Mars but far denser, so the two come out within a thousandth of each other. Saturn is vast but extraordinarily diffuse, so it barely matches Earth.
For Jupiter, Saturn, Uranus and Neptune there is no surface to stand on. Their figures are taken at the cloud tops, the level where the atmospheric pressure equals Earth's at sea level, which is the usual convention. The Sun's figure is real but academic: its visible surface is 5,500°C plasma.
One more wrinkle worth knowing about. The factors here are NASA's ratio-to-Earth values, which include the effect of each body's rotation. Spin flings you outwards very slightly, so a fast-rotating planet holds you down a little less than its mass and radius alone suggest. It barely matters for the rocky worlds, but Jupiter turns once every ten hours, and that is enough to drop its equatorial figure from 2.53 to 2.36. Since a set of scales measures the force it actually feels, the rotation-adjusted number is the one you want — you will see the higher figures quoted elsewhere, and neither is wrong, they are just answering slightly different questions.
Worked example
Take someone who weighs 70 kg on Earth. Multiply straight through by each factor:
Moon: 70 × 0.166 = 11.6 kg
Mars: 70 × 0.377 = 26.4 kg
Saturn: 70 × 0.916 = 64.1 kg — nearly six kilos lighter than at home
Jupiter: 70 × 2.36 = 165.2 kg
The Sun: 70 × 27.9 = 1,953 kg
In every one of those cases the person is still made of exactly the same amount of stuff. Only the force pulling on it has changed.
Mass and weight are not the same thing
This is the distinction the whole page rests on. Mass is how much matter you are made of, measured in kilograms. It is a property of you, and it does not change when you travel — you would have the same mass on Pluto, on Jupiter, or drifting in deep space.
Weight is a force: the pull that a nearby massive object exerts on your mass. Its proper unit is the newton. That force depends entirely on what you are standing near, which is why it changes from world to world while your mass stays put.
Everyday language blurs the two, and so do bathroom scales — they measure force and then display it in kilograms, quietly assuming Earth's gravity. This calculator follows the same convention, showing your results in whichever unit you entered, because "you'd be 11.6 kg on the Moon" is what people actually want to know. Strictly, that is the mass which would weigh the same on Earth as you do on the Moon.
Gravity factors used
| Body | Gravity (Earth = 1) | Body | Gravity (Earth = 1) |
|---|---|---|---|
| Pluto | 0.063 | Venus | 0.907 |
| Titan | 0.138 | Saturn | 0.916 |
| Ganymede | 0.146 | Earth | 1.000 |
| The Moon | 0.166 | Neptune | 1.12 |
| Mars | 0.377 | Jupiter | 2.36 |
| Mercury | 0.378 | The Sun | 27.9 |
| Uranus | 0.889 | — | — |
Planetary figures are NASA's ratio-to-Earth surface gravity values from the NSSDCA Planetary Fact Sheet. Titan and Ganymede are worked out from their measured surface gravities of 1.352 and 1.428 m/s² against Earth's 9.807.
Frequently asked questions
Would I really weigh less on Saturn than on Earth?
Yes, marginally — about 8% less at the cloud tops. Saturn has ninety-five times Earth's mass, but that mass is spread across a ball more than nine times wider, and gravity falls off with the square of the distance from the centre. Saturn's average density is less than water's, so it would float in a big enough bath. The catch is that there is no cloud-top surface to stand on, and the temperature and winds there are lethal.
Does my mass change on another planet?
No. Mass is the amount of matter you are made of and it travels with you unchanged. Only your weight — the force gravity exerts on that mass — varies from place to place. An astronaut floating in orbit is weightless but has exactly the mass they had at launch, which is why bumping into something up there still hurts.
Why show weights in kilograms if a kilogram is a unit of mass?
Because it is what everyone means in practice. The strictly correct unit of weight is the newton, but bathroom scales measure force and convert it to kilograms assuming Earth's gravity. Reading "11.6 kg on the Moon" as "what the scales would say if you took them with you" is the sense intended here, and it is the same convention every set of scales already uses.
Could you actually stand on Jupiter, Saturn or the Sun?
No. Jupiter, Saturn, Uranus and Neptune have no solid surface — the atmosphere simply gets denser with depth until it stops being a gas, so the figures here are quoted at the cloud tops by convention. The Sun is worse still: its visible surface is 5,500°C plasma, so its 27.9 figure is there for scale rather than as a travel plan.
Why is Mercury's gravity almost identical to Mars's when Mercury is so much smaller?
Because gravity depends on density as well as size. Mercury is just under three-quarters of Mars's diameter but far denser, with an enormous iron core taking up most of its volume — it is the second densest body in the solar system after Earth. Those two effects very nearly cancel out. Mars then loses a fraction more to its own rotation, which is what tips the final order: Mercury 0.378, Mars 0.377.
What would I weigh on the Moon?
About a sixth of your Earth weight — the factor is 0.166. An 80 kg person comes out at roughly 13.3 kg, or 12 stone becomes just under 2 stone. That is why the Apollo astronauts bounced rather than walked, even wearing suits and life support that weighed more than they did on Earth.