Why does weight change on other planets but mass doesn't?

Mass is the amount of matter in an object and stays constant everywhere. Weight is the gravitational force on that mass (Weight = Mass × g), so it changes with the local gravitational acceleration, which differs from planet to planet (e.g. about 3.7 m/s² on Mars vs 9.8 m/s² on Earth).

What does the 'kgf' unit in the result mean?

kgf (kilogram-force) is the everyday 'weight in kilograms' figure most people are used to, calculated by dividing the newton result by standard Earth gravity (9.80665 m/s²). It's shown alongside newtons since newtons are the correct SI unit for force.

Mass to Weight Calculator

Convert mass to weight (force) on Earth or other planets.

How this is calculated

Weight = Mass × local gravitational acceleration

Assumptions used in this calculation

Standard surface gravity values: Uses published mean surface gravitational acceleration for each body (9.80665 m/s² for Earth), not adjusted for altitude, latitude or local geological variation.
Point-mass gravity: Treats the object as resting on the planet's surface under uniform gravity, ignoring altitude above the surface or orbital effects.

About this calculator

The mass to weight calculator converts a fixed mass into its weight (a force, in newtons) at the surface of Earth or another planet or moon, using local gravitational acceleration.

Worked example

70 kg on Earth

Result: 686.7 N (70 kgf)

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About this calculator

Frequently asked questions

Why does weight change on other planets but mass doesn't?

What does the 'kgf' unit in the result mean?

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