The planet weight calculator above scales your Earth weight by the ratio of surface gravities. It covers the eight planets, the Moon, Pluto and the visible surface of the Sun, and it shows the gravity figure behind every answer so you can check the arithmetic rather than trusting it.
Arb Digital publishes free physics tools that get the underlying ideas right rather than just producing a number. The one this page is built on is the distinction between mass and weight, which almost every version of this calculator elsewhere quietly ignores.
What This Planet Weight Calculator Does
You enter a weight in kilograms, pounds or stone. The tool converts it to a mass, multiplies by the surface gravity of each body, and converts back so the answers appear in the same unit you typed. The chosen body fills the headline, and the bar list underneath compares every body at once.
The grid adds four figures. Surface gravity is the acceleration in metres per second squared at that body's surface, which is the quantity everything else derives from. The ratio to Earth is the same number divided by 9.80665, and it is the multiplier applied to your weight. The force in newtons is what a spring balance on that world would actually be measuring. And your mass is shown deliberately unchanged, because that is the point.
Gravity is quoted at the equator, and for the gas and ice giants at the visible cloud tops rather than any solid surface, because none of them has one. Standing on Jupiter is not a thing you could do; the figure tells you the local acceleration if you could hover there.
How to Use It
- Type the number your scale shows. There is no need to convert anything first — the tool handles kilograms, pounds and stone internally.
- Pick a body for the headline. The full comparison list appears whichever one you choose, so the selection is only about which figure gets the large type.
- Look at the ratio, not just the weight. The ratio to Earth is the transferable number: it applies equally to a person, a spacecraft, or a hammer.
- Read the newton figure to see what is really happening. Weight is a force. The newton value is the physical quantity; the kilogram reading is a convention that assumes Earth gravity.
- Notice which bodies surprise you. Mars and Mercury come out almost identical despite Mars having nearly twice the mass. The reason is explained below.
The Formula: Why Weight Changes and Mass Does Not
Mass is the amount of matter in you, measured in kilograms, and it is the same everywhere in the universe. Weight is the gravitational force acting on that mass, W = mg, measured in newtons. A bathroom scale measures force and then divides by Earth's gravity to display something that looks like a mass. Take the same scale to Mars and it reads low, not because you have lost matter but because the force has shrunk.
Surface gravity itself comes from Newton's law of gravitation applied at the surface: g = GM ÷ R2, where M is the body's mass, R its radius, and G the gravitational constant, 6.674 × 10−11 N·m²/kg². OpenStax University Physics Volume 1, section 13.2 on gravitation near Earth's surface, derives that relationship and shows how it lets a planet's mass be worked out from its surface gravity.
The gravity figures for the planets and for Pluto come from Planetary Physical Parameters, published by the NASA Jet Propulsion Laboratory Solar System Dynamics group. The Moon and the Sun are computed here from the same equation using a lunar mass of 7.346 × 1022 kg with a radius of 1,737.4 km, and a solar mass of 1.9884 × 1030 kg with a radius of 695,700 km.
Work the default through. A 70 kg person on Mars, where g is 3.71 m/s². The ratio to Earth is 3.71 ÷ 9.80665 = 0.3783. Multiply: 70 × 0.3783 = 26.5 kg on a Martian scale. As a force, 70 × 3.71 = 259.7 N, against 686.5 N on Earth. The mass is still 70 kg in both places.
Why Mars and Mercury Feel the Same Despite Being Very Different
Mercury has about 55 per cent of Mars's mass, yet the two have nearly identical surface gravity, around 3.7 m/s². The reason is in the denominator. Mercury is also much smaller, with a radius of about 2,440 km against Mars's 3,390 km, and radius enters the equation squared. Standing on Mercury puts you closer to its centre, which compensates almost exactly for its lower mass.
The same effect runs the other way for the giants. Saturn is 95 times the mass of Earth but its surface gravity is only about 1.07 times Earth's, because its cloud tops sit more than nine Earth radii from its centre. Uranus, at 14 Earth masses, actually has slightly less surface gravity than Earth. Mass alone tells you very little about what you would feel standing there.
Jupiter is the exception that proves the rule: it is massive enough, at 318 Earth masses, that even an eleven-fold radius cannot cancel it, and it comes out at about 2.5 times Earth gravity. The Sun goes further still, at roughly 28 times Earth gravity, which would turn a 70 kg person into a 1,960 kg one.
What Changes With Your Weight, and What Does Not
Lower gravity changes some things dramatically and leaves others untouched, and the split is not obvious.
How high you can jump scales inversely with gravity, so an athlete who clears half a metre on Earth would clear about three metres on the Moon. How fast you can throw something does not change at all, because that depends on muscle and mass rather than gravity; the projectile simply travels much further before landing. How much you can lift changes, because lifting works against weight. How much you can push a heavy object sideways barely changes, because that fights inertia, which depends on mass.
Falling is slower everywhere except the giants. A drop that takes one second on Earth takes about 2.5 seconds on the Moon, and the impact speed is correspondingly lower. Our free fall calculator works those times out for any gravity you give it.
The one that catches everybody: your weight in orbit is not zero because gravity has stopped. At the altitude of the International Space Station, Earth's gravity is still about 89 per cent of its surface value. Astronauts float because they and the station are falling around the Earth together, not because the pull has gone. That orbital condition is what the orbital velocity calculator quantifies.
Where This Sits Beside Our Other Gravity Tools
This page does one thing: it rescales a weight between surfaces using published gravity values. For the force between any two masses at any separation, rather than a body sitting on a surface, use the gravitational force calculator. To find how fast you would have to travel to leave a body entirely, use the escape velocity calculator, and for the speed and period of a circular orbit around one, the orbital velocity calculator. The relationship between orbital period and distance for moons and planets belongs to the Kepler's third law calculator.
If you need to move between pounds, kilograms and stone before or after, the weight converter handles it, and the force converter takes newtons into pounds-force and kilograms-force.
Arb Digital builds free tools like this one because useful pages earn attention. If you want tools, calculators or content built for your own audience, we can help.
Browse All Free Tools Talk to Arb DigitalCommon Mistakes to Avoid
- Saying your mass changes on another planet — it does not. Only the gravitational force on it changes, and with it what a scale reads.
- Assuming a more massive planet always means heavier — Uranus has fourteen times Earth's mass and slightly weaker surface gravity, because its radius is four times larger and radius enters squared.
- Expecting a solid surface on the giants — the quoted gravity for Jupiter, Saturn, Uranus and Neptune is at the visible cloud tops. There is nothing to stand on.
- Thinking gravity is absent in orbit — at station altitude Earth's pull is still about 89 per cent of its surface value. Astronauts float because they are in continuous free fall, not because gravity stopped.
- Ignoring rotation and latitude — published surface gravity is usually equatorial, where a body's spin reduces the effective value slightly. Earth's own gravity varies by about half a per cent from equator to pole.
Related Free Tools From Arb Digital
For the attraction between any two masses, use the gravitational force calculator. To find the speed needed to break free of a body, use the escape velocity calculator, and for circling it instead, the orbital velocity calculator. Orbital periods and distances are handled by the Kepler's third law calculator, and falling times under any gravity by the free fall calculator. Convert the numbers with the weight converter and the force converter. Everything Arb Digital publishes is at the free online tools hub.
Frequently Asked Questions
No. Mass is the amount of matter in you and it is identical everywhere. What changes is weight, the gravitational force acting on that mass, which is why a scale gives a different reading. A 70 kilogram person is 70 kilograms of matter on Earth, on Mars and in deep space.
Mercury has roughly 55 per cent of Mars's mass but a much smaller radius, about 2,440 kilometres against 3,390. Surface gravity divides mass by radius squared, so being closer to the centre compensates almost exactly for having less mass. Both come out near 3.7 metres per second squared.
About 28 times your Earth weight, since solar surface gravity is roughly 274 metres per second squared. That figure is at the visible photosphere, which is not a surface in any useful sense, and the temperature there is around 5,500 degrees Celsius, so the number is a thought experiment.
No. They have no solid surface, so the gravity figures quoted for them apply at the visible cloud tops. Below that the atmosphere simply grows denser until it merges continuously into a fluid interior, with no boundary to stand on at any depth.
Because they are in free fall. At the International Space Station's altitude Earth's gravity is still about 89 per cent of its surface value, but the station and everyone in it are falling around the planet at the same rate, so nothing pushes back against them and there is no sensation of weight.
Roughly six times as high, since lunar gravity is about one sixth of Earth's and jump height scales inversely with gravity. A half-metre standing jump becomes about three metres. A spacesuit's mass and stiffness cut that back considerably in practice.
The eight planets and Pluto use the equatorial gravity figures published by NASA's Jet Propulsion Laboratory in its Planetary Physical Parameters table. The Moon and the Sun are computed from their published masses and radii using Newton's law of gravitation, which is the same relationship those tabulated values are derived from.
This tool is provided for educational use. Surface gravity values are equatorial and, for the giant planets and the Sun, refer to the visible outer layer rather than any solid surface. Local gravity on a real body also varies with latitude, altitude and subsurface density.
