To calculate mass and weight on different planets, take an Earth scale reading and multiply it by each planet's surface gravity divided by Earth's gravity — this is NASA's W = mg formula applied to every world in turn. NASA expresses the relationship as W = mg, where weight equals mass multiplied by gravitational acceleration, and the calculator applies the same ratio to Mercury, Venus, Mars, Jupiter, Saturn, Uranus, and Neptune using published equatorial gravity values. Mass itself does not change as you travel, only the force that pulls on it, so the result is a familiar scale-equivalent reading rather than a true change in how much matter you carry. JPL publishes the underlying gravitational accelerations used here: 3.70 m/s² for Mercury, 8.87 for Venus, 9.80 for Earth, 3.71 for Mars, 24.79 for Jupiter, 10.44 for Saturn, 8.87 for Uranus, and 11.15 for Neptune. Plug any of those into the ratio above and you reproduce the same educational numbers NASA uses — a 100-unit Earth reading comes out to roughly 38 on Mercury and roughly 253 on Jupiter.
Mass vs Weight: What Actually Changes on Another Planet
Mass is the amount of matter in an object and stays the same wherever the object goes. Weight is a force — the pull of gravity on that mass — and it changes whenever gravity changes. NASA summarizes this with W = mg, where W is weight, m is mass, and g is gravitational acceleration at the location. On Earth, g is about 9.80 m/s². On the Moon, g is about 1.62 m/s². On Jupiter's equatorial reference level, g is about 24.79 m/s². Same person, same mass, very different weight.
This distinction matters for the calculator. If you step on a bathroom scale on Earth, the scale reads your Earth weight. The scale does not directly know your mass; it measures the downward force and infers a mass by dividing through Earth gravity. A kilogram-labeled bathroom scale is really a force-measuring device with an internal Earth-gravity assumption baked in. That is why the calculator lets you keep kilograms as the display label even though the underlying ratio is unitless. The displayed kilogram result is a familiar scale-equivalent reading, not a claim that your mass changed. The same numeric comparison can be expressed in pounds, newtons, or a custom unit because gravity ratios do not depend on any particular unit.
Using the Weight on Other Planets Calculator
- Enter a positive scale reading measured on Earth. Use the number you normally see when you weigh yourself. A 70 kg bathroom reading or a 154 lb reading both work; the calculator accepts any positive value with the unit label you choose.
- Choose a display label, then select Compare planetary weight. The label tells the tool how to phrase the output (pounds, kilograms, newtons, or a custom unit). The compare action triggers the side-by-side table of all eight planets.
- Read each planet's equatorial gravity and equivalent value. The table lists Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune in order. Each row shows the planet, its surface gravity in m/s², and the equivalent weight under your chosen label.
The table runs locally and does not store your personal measurements. Changing the input clears the previous table so a stale comparison is not mistaken for a new one. For a quick sanity check before reading the table, confirm that the Earth row equals the value you typed in. Then check that Mercury is roughly a third of your Earth reading and Jupiter is roughly two and a half times larger — those two reference points are NASA's own educational anchors.
JPL Equatorial Gravity Reference Values
The reference table comes from the NASA/JPL Solar System Dynamics planetary physical parameters page. The values used are equatorial surface gravity for each of the eight IAU-recognized planets, expressed in m/s²:
| Planet | Equatorial gravity (m/s²) |
|---|---|
| Mercury | 3.70 |
| Venus | 8.87 |
| Earth | 9.80 |
| Mars | 3.71 |
| Jupiter | 24.79 |
| Saturn | 10.44 |
| Uranus | 8.87 |
| Neptune | 11.15 |
These are published JPL equatorial values, not exact readings at every location on each planet. Real effective gravity varies with latitude, altitude, rotation, and local geology. For a person standing at the equator, the value is close to the table; for the same person at the pole, it is slightly higher because the pole is closer to the spin axis and centrifugal reduction is smaller. The table also uses different conventions for gas and ice giants, which have no solid surface. JPL's value for Jupiter, Saturn, Uranus, and Neptune is associated with a defined reference level rather than a place where someone could stand.
A Worked Example: 100 on Earth
For a single concrete calculation, take an Earth reading of 100 in whatever label you prefer — pounds, kilograms, newtons, or otherwise. The formula for each planet is the same ratio:
Equivalent = Earth reading × (planet gravity / Earth gravity)
Take Mercury, which has an equatorial gravity of 3.70 m/s² against Earth's 9.80 m/s²:
Equivalent on Mercury = 100 × (3.70 / 9.80) = 100 × 0.3776 = 37.76
That matches NASA's familiar educational anchor: a person who "weighs" 100 on Earth would weigh roughly 38 on Mercury. Take Jupiter for the upper bound:
Equivalent on Jupiter = 100 × (24.79 / 9.80) = 100 × 2.5296 = 252.96
Again, that matches the standard NASA educational example of roughly 253 on Jupiter. These two checks — Mercury ≈ 38 and Jupiter ≈ 253 for an Earth reading of 100 — are how the calculator is validated against NASA's published comparisons. Repeat the substitution for any other planet using the table above if you want to confirm the pattern by hand.
Why These Numbers Are Educational Approximations
The calculator rounds each result to a practical decimal. That is deliberate. The JPL source values are themselves rounded, and local gravity varies in the ways already described, so adding more decimal places would create a false impression of precision. For classroom work, the right citation is the JPL planetary physical parameters page along with the explicit note that the comparison uses equatorial gravity.
The numbers are also limited to the eight IAU-recognized planets. The Moon, Pluto, dwarf planets, asteroids, stars, and exoplanets are out of scope by design. The tool does not calculate gravitational force from arbitrary mass and radius, escape velocity, orbital weightlessness, atmospheric buoyancy, or biological effects on the body. It is not a health, fitness, or dosing calculator, even if the starting number happens to come from a bathroom scale.
A useful mental model: the comparison tells you what a household scale would read if you could step onto that world under Earth-like conditions at the equator. Real spacecraft trajectories, atmospheric motion, free fall, and surface conditions all require a more complete physical model. The numbers shown here are enough to make a planetary comparison vivid, and no more.
When You Need a More Detailed Model
For engineering or mission analysis, swap this calculator for a body-specific gravity model. That model would account for altitude above the reference ellipsoid, the planet's actual shape, latitude-dependent corrections, rotation, and the uncertainty required by the project. NASA's JPL Planetary Physical Parameters page is the public source for the gravity values used here; for higher-fidelity work, NASA's Navigation and Mission Design tools provide full reference models. NASA's Space Place page on planetary weight is a classroom-level primer that walks through the same comparison in plain language.
The underlying physics is straightforward. The conversion between mass and weight is the W = mg relationship applied at a different g value. Run the same input through different g values and you get the planet-by-planet comparison automatically. Mass does not change; the gravitational acceleration does.
To compare a starting Earth scale reading across all eight planets at once, the Weight on Other Planets Calculator uses these JPL equatorial gravity values directly. Enter a positive Earth reading, pick your label, and the table shows Mercury through Neptune with the rounded equivalent next to each planet's gravity. Confirm the Earth row matches your input, then glance at Mercury and Jupiter as a quick reasonableness check before using the remaining educational values.