Weight Calculator

The Formula

Weight is the force of gravity acting on a mass. On Earth, gravity pulls at 9.81 m/s², so a 70 kg person weighs 686.7 N (about 154 lbf). On the Moon, the same person would weigh only 113.4 N.

Variable Definitions

How to Use This Calculator

1. 1

   Select what you want to solve for: Weight, Mass, or Gravity.

2. 2

   Choose a gravity preset (Earth, Moon, Mars, Jupiter, Sun) or enter a custom value.

3. 3

   View the result in Newtons and pounds-force, plus a comparison across planets.

Weight (W = m × g) changes with gravity while mass stays constant across planets.

Understanding the Concept

Weight is not the same as mass. Weight is the force exerted by gravity on a mass: W = mg. While mass is constant, weight changes depending on where you are. On Earth, g = 9.81 m/s². The Moon has g = 1.62 m/s² (about 1/6 of Earth), and Jupiter has g = 24.79 m/s² (about 2.5× Earth). A 70 kg person weighs 686.7 N on Earth, but only 113.4 N on the Moon and a crushing 1735.3 N on Jupiter. Practical example: if you weigh 154 lbs on Earth (about 70 kg), your weight in Newtons is 70 × 9.81 = 686.7 N. To convert Newtons to pounds-force, multiply by 0.224809: 686.7 × 0.224809 = 154.3 lbf. On Mars (g = 3.71 m/s²), the same person weighs 70 × 3.71 = 259.7 N, or about 58.4 lbf — that is only 38% of your Earth weight. Edge cases: astronauts in orbit around Earth experience microgravity not because gravity is absent (gravity at the ISS altitude is still about 90% of surface gravity) but because they are in continuous free fall. Their apparent weight is near zero, but their mass is unchanged. For extremely precise measurements, gravity varies by location on Earth — it is about 9.78 m/s² at the equator and 9.83 m/s² at the poles due to Earth's rotation and equatorial bulge. Elevation also matters: at 5,000 meters, gravity is about 9.79 m/s². For springs and force gauges, weight is the force that stretches or compresses them. A spring scale calibrated on Earth would give incorrect readings on the Moon because it measures force (weight), not mass. A balance scale, which compares masses, would give the same reading anywhere.

Frequently Asked Questions

Sources & References