Weight Calculator
Calculate weight as gravitational force (F = m x g) from mass and a selected gravity — Earth, Moon, Mars, or custom.
How It's Calculated
Formula
F = m \times gWeight, in the physics sense, is the gravitational force acting on a mass: F = m x g, where m is mass in kilograms and g is gravitational acceleration in meters per second squared, giving a result in newtons (N). This is distinct from mass, which is the amount of matter an object contains and does not change with location (see the separate Mass Calculator). Standard Earth gravity is g0 = 9.80665 m/s2, the internationally defined standard gravity constant (3rd CGPM, 1901). Moon and Mars presets use commonly published surface gravity values (1.62 m/s2 and 3.71 m/s2 respectively); a Custom option accepts any other positive gravitational acceleration. This calculator is not the same as the Weight/Mass Converter, which only re-expresses an already-known mass value in a different unit and never computes a force, and it is not a body-weight or health calculator.
Worked Examples
1 kg on Earth
- Weight = 1 kg x 9.80665 m/s2 = 9.80665 N.
100 kg on Earth
- Weight = 100 kg x 9.80665 m/s2 = 980.665 N.
Frequently Asked Questions
Is this the same as the Weight/Mass Converter?
No. This calculator computes weight as a gravitational force (F = m x g) in newtons from a mass and a gravity value. The Weight/Mass Converter instead re-expresses an already-known mass value in a different unit (for example, kilograms to pounds) and never computes a force.
Why does weight change between Earth, Moon, and Mars but mass doesn't?
Mass is the amount of matter in an object and is the same everywhere. Weight is the gravitational force on that mass, which depends on local gravitational acceleration — the Moon's gravity (1.62 m/s2) is much weaker than Earth's (9.80665 m/s2), so the same mass weighs less there.
Why is standard Earth gravity 9.80665 and not 9.8 or 9.81?
9.80665 m/s2 is the internationally defined standard gravity constant, fixed by the 3rd General Conference on Weights and Measures (CGPM) in 1901. 9.8 and 9.81 are common rounded approximations; this calculator uses the exact defined value by default.
Is this a body-weight or health calculator?
No. This is a physics force calculation only. It does not compute body mass index, healthy weight ranges, or any health-related metric.