Weight Calculator
Calculate weight force from mass and gravitational acceleration.
Calculate weight force (in newtons) from an object's mass and the local gravitational acceleration — useful for physics problems and comparing weight across planets.
How Weight Calculator Works
In physics, weight is a force, not the same thing as mass. It's calculated as weight = mass × gravitational acceleration (Newton's second law, F = ma applied to gravity), which is why the result is expressed in newtons (N), the standard unit of force, rather than kilograms.
The default gravitational acceleration, 9.80665 m/s², is standard Earth gravity at sea level. Changing this value lets you calculate weight force on other bodies — the Moon's gravity is about 1.62 m/s², and Mars' is about 3.71 m/s², both much lower than Earth's.
See It In Action
Who Uses Weight Calculator and Why
- Calculating how much less a known mass would weigh on the Moon or Mars compared to Earth for a physics assignment or curiosity.
- Working out the weight force (in newtons) of an object for an engineering or structural calculation.
- Understanding the distinction between mass and weight for a physics course.
- Checking a textbook problem that gives mass and asks for the gravitational force acting on it.
Mistakes to Avoid
- Treating the newton result as interchangeable with the everyday "weight in kilograms" shown on a bathroom scale — a scale actually displays a mass reading calibrated for Earth gravity, while this calculator gives the actual force in newtons.
- Forgetting to change the gravity value when calculating weight on another body — leaving it at Earth's default 9.80665 m/s² while intending to compute lunar or Martian weight gives a result that's still just Earth weight.
- Assuming mass and weight are the same thing and using them interchangeably in a physics problem — mass never changes with location, but weight force does.
Tips for Best Results
- Use 9.80665 m/s² for standard Earth gravity, about 1.62 m/s² for the Moon, and about 3.71 m/s² for Mars if comparing weight across bodies.
- To convert the newton result to pounds-force for comparison with imperial figures, divide by about 4.448.
Fixing Common Problems
My result seems too large a number to be a normal 'weight'. — That's expected — newtons are a smaller unit than kilograms-force, so a typical adult's weight force is around 700-800 N rather than the 70-80 kg figure a bathroom scale shows.
I want the weight in pounds, not newtons. — Divide the newton result by approximately 4.448 to convert to pounds-force (lbf).
Terms Explained
Weight: The force gravity exerts on an object's mass, calculated as mass × gravitational acceleration and measured in newtons.
Gravitational acceleration (g): The rate at which gravity accelerates a falling object at a given location — about 9.80665 m/s² at Earth's surface, and lower on smaller bodies like the Moon or Mars.