Quick answer: Weight is mass times gravity: a 70 kg person weighs 70 × 9.80665 = 686.47 N on Earth and 70 × 1.62 = 113.4 N on the Moon.
How it's calculated
Weight is the force of gravity on a mass: W = m × g. With mass in kilograms and g in m/s², the weight is in newtons (N).
On Earth the calculator uses standard gravity, g₀ = 9.80665 m/s², the value fixed by international agreement. Real gravity varies a little with latitude and height, from about 9.78 at the equator to 9.83 at the poles.
A kilogram-force (kgf) is the weight of 1 kg under standard gravity, 9.80665 N, and a pound-force (lbf) is 4.448 N. The scale-reading column shows what a bathroom scale calibrated on Earth would show elsewhere. Planet values are surface (or 1-bar) gravity from NASA's fact sheets.
Worked examples
- 70 kg on Earth: 70 × 9.80665 = 686.47 N
- 70 kg on Mars: 70 × 3.71 = 259.7 N (a scale shows 26.5 kg)
- 1,000 kg car on Earth: 1,000 × 9.80665 = 9,806.65 N ≈ 9.81 kN
Surface gravity
| Body | g (m/s²) | Relative to Earth |
|---|---|---|
| Earth (standard) | 9.80665 | 1 |
| Moon | 1.62 | 0.165 |
| Mercury | 3.7 | 0.377 |
| Venus | 8.87 | 0.904 |
| Mars | 3.71 | 0.378 |
| Jupiter | 24.79 | 2.528 |
| Saturn | 10.44 | 1.065 |
| Uranus | 8.87 | 0.904 |
| Neptune | 11.15 | 1.137 |
| Pluto | 0.62 | 0.063 |
Frequently asked questions
What is the difference between mass and weight?
Mass (kg) is the amount of matter and is the same everywhere. Weight (N) is the gravitational force on it and changes with gravity: you weigh about one-sixth as much on the Moon.
What is the value of g?
Standard gravity is 9.80665 m/s². In school problems 9.8 or 9.81 is often used.
How many newtons is 1 kg?
1 kg has a weight of 9.80665 N on Earth, also called 1 kilogram-force.
How much would I weigh on the Moon?
About a sixth of what you weigh here. Someone who's 70 kg would see roughly 11.6 kg on an Earth-calibrated bathroom scale.
What is a kilonewton?
1,000 newtons, or about the weight of 102 kg on Earth. You'll see it on lifting gear, anchors and beam loads.
Why does a scale show kg if weight is a force?
Bathroom scales measure force and divide it by standard gravity to give you a mass. That's why the reading would change on the Moon even though you wouldn't.