Weight Calculator
Calculate the gravitational force (weight) on any mass using W = m·g.
How it works
- 1Enter the object’s mass in kg (or lb in imperial mode) and the gravitational acceleration g.
- 2The calculator converts your inputs to SI units and applies W = m·g to find the weight in newtons.
- 3Results are shown in your chosen unit system (N or lbf) plus secondary displays in N and kgf.
Use cases
- Engineering loads — find the force a structure must support for a known mass.
- Space and planetary science — swap in the surface gravity of the Moon (1.62 m/s²) or Mars (3.71 m/s²) to compare weights.
- Physics homework — quickly verify W = m·g calculations with a worked unit breakdown.
Frequently asked questions
What is the formula for weight?
Weight W = m·g, where m is mass in kilograms and g is gravitational acceleration in m/s². On Earth’s surface g ≈ 9.80665 m/s², so a 70 kg person has a weight of 70 × 9.80665 ≈ 686.5 N.
What is the difference between mass and weight?
Mass (kg) is a fixed measure of how much matter an object contains — it never changes. Weight (N) is the gravitational force on that mass and depends on location: the same 70 kg person weighs 686 N on Earth but only 113 N on the Moon (g ≈ 1.62 m/s²).
Why can I change g in this calculator?
Standard gravity (9.80665 m/s²) applies at sea level on Earth. To find weight on other planets or at altitude, enter a different g — for example, 3.71 m/s² for Mars — to get the correct weight for that environment.
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