About the Weight on Other Planets Calculator
A free, instant calculator that shows your weight across two named planetary systems — Our Solar System and the real TRAPPIST-1 exoplanet system.
What it is
The Weight on Other Planets Calculator takes a single weight value — in kg, lb, or stone — and immediately shows you the equivalent weight on every body in the chosen planetary system. Switch between Our Solar System (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, the Moon, the Sun, and Pluto) and the TRAPPIST-1 System (seven rocky exoplanets orbiting an ultracool dwarf star ~39 light-years away). Your entered weight and unit are preserved when you switch systems — results update live as you type.
Everything runs in your browser. Your weight is never sent to a server or stored anywhere — close the tab and it is gone.
Key features
Two named planetary systems
Switch between Our Solar System (11 bodies) and the real TRAPPIST-1 System (7 exoplanets) with a single tap. Weight and unit are preserved across both systems.
Real exoplanet gravity data
TRAPPIST-1 planets are included because both their mass and radius have been precisely measured — so the weights shown are based on real science, not approximations.
kg, lb, and stone switching
Switch freely between kilograms, pounds, and stone. Your input auto-converts when you change units so you never need to re-type your weight — works across both systems.
Gravity comparison per body
Each card shows the gravity multiplier and a proportional bar so you can instantly compare gravitational strength — within and between planetary systems.
Mass versus weight
Your mass — the amount of matter that makes you up — is constant everywhere in the universe. Weight is the force of gravity on that mass, measured in newtons (or colloquially in kg/lb/st). Because gravitational pull varies from world to world, your weight changes while your mass does not. On the Moon you'd weigh about one-sixth of your Earth weight; on Jupiter you'd weigh more than twice as much.
The TRAPPIST-1 System
TRAPPIST-1 is an ultracool M-dwarf star about one-tenth the mass and size of our Sun, located ~39 light-years away in Aquarius. It hosts seven known rocky planets, all in or near its habitable zone. What makes this system special for this tool is that the TRAPPIST-1 planets are among the most precisely characterised exoplanets known — both mass (from transit timing variations) and radius (from transit photometry) have been measured for all seven, allowing surface gravity to be reliably computed.
TRAPPIST-1 e has gravity closest to Earth's (~0.91×) — the most Earth-like world in the system by this measure. TRAPPIST-1 d has the lowest gravity (~0.48×). In reality, several of these planets may be tidally locked, frozen, or have thick atmospheres — the weights shown are a hypothetical comparison of gravitational pull, not an assessment of habitability.
Who it's for
Students
Understand the difference between mass and weight hands-on, explore real exoplanet data, or verify homework answers about planetary gravity.
Teachers
Project the calculator on screen to make gravity tangible — enter a student's weight and let them see how it would change on Mars, Jupiter, or a real exoplanet.
Space enthusiasts
Explore what daily life might feel like under different gravitational conditions, from Pluto's feather-light pull to the crushing weight of the Sun.
Curious kids
A fun, no-jargon way to explore the solar system and beyond — enter your weight and discover where in the universe you'd feel the lightest.
Gravity ratios used
Each result is your Earth weight multiplied by the body's surface-gravity ratio relative to Earth's 9.807 m/s². For gas giants, "surface" gravity is measured at the cloud-top level; for the Sun, it is at the photosphere.
Our Solar System
| Body | Gravity ratio | Type |
|---|---|---|
| Mercury | ×0.378 | Rocky planet |
| Venus | ×0.907 | Rocky planet |
| Earth | ×1.000 | Reference |
| Moon | ×0.165 | Natural satellite |
| Mars | ×0.377 | Rocky planet |
| Jupiter | ×2.360 | Gas giant (cloud top) |
| Saturn | ×0.916 | Gas giant (cloud top) |
| Uranus | ×0.889 | Ice giant (cloud top) |
| Neptune | ×1.120 | Ice giant (cloud top) |
| Pluto | ×0.063 | Dwarf planet |
| Sun | ×27.900 | Star (photosphere) |
TRAPPIST-1 System
| Body | Gravity ratio | Note |
|---|---|---|
| TRAPPIST-1 b | ×0.817 | Rocky exoplanet |
| TRAPPIST-1 c | ×0.961 | Rocky exoplanet |
| TRAPPIST-1 d | ×0.478 | Lowest gravity in system |
| TRAPPIST-1 e | ×0.912 | Most Earth-like gravity |
| TRAPPIST-1 f | ×0.855 | Rocky exoplanet |
| TRAPPIST-1 g | ×0.901 | Rocky exoplanet |
| TRAPPIST-1 h | ×0.581 | Rocky exoplanet |
TRAPPIST-1 gravity ratios are computed from measured mass and radius values in: Agol, E. et al. (2021) "Refining the Transit-timing and Photometric-dynamical Model of the TRAPPIST-1 Planetary System", PSJ 2:1, doi:10.3847/PSJ/abd022. These are best estimates — exoplanet measurements carry inherent uncertainty and values may be refined as new data becomes available.
How the calculation works
The tool converts your input to kilograms, multiplies by each body's gravity ratio, then converts back to your chosen unit. The formula is: weight_on_body = weight_earth_kg × gravity_ratio, then converted to lb or stone if needed.
Unit conversions use exact factors: 1 kg = 2.20462 lb and 1 stone = 6.35029 kg. Switching units auto-converts your input through the same chain so round-trip accuracy is preserved. Both planetary systems share the same input and unit state — switching systems never changes your entered weight or unit.
Completely free
No sign-up, no rate limit, no premium tier. Enter any weight — integer, decimal, or very large — and the calculator handles it instantly. If you find it useful, share it with a classmate or friend.