Weight Force Calculator
Enter a mass and the local gravitational acceleration to get the weight force in newtons — the gravitational pull on the object — and see how the same mass weighs differently on the Moon or Mars.
Weight in newtons
Enter the mass and the local gravity and the calculator returns the weight force (W = mg) in newtons — the force gravity exerts on the object.
Use SI units
Mass in kilograms and gravity in metres per second squared give the weight in newtons. Earth gravity is about 9.80665 m/s²; the Moon is roughly 1.62.
What does the weight force calculator do?
The gravitational pull on a mass
The weight force calculator turns a mass and a gravitational acceleration into the weight force — the downward pull that gravity exerts on an object — measured in newtons. This is what a bathroom scale really senses and what an engineer calls the load a structure must support. The key idea is that mass and weight are not the same thing: mass (in kilograms) is the amount of matter and never changes, while weight (in newtons) is a force that depends on where you are. The same 70 kg person weighs about 686 N on Earth but only about 113 N on the Moon, because the Moon's gravity is far weaker.
Enter a mass in kilograms and a gravity in metres per second squared to get the weight force in newtons instantly.
The weight force is simply the mass multiplied by the local gravitational acceleration.
W = m × gHere m is the mass in kilograms and g is the gravitational acceleration in metres per second squared. On the surface of the Earth g is about 9.80665 m/s², the standard value used worldwide. To find the weight of a 70 kg person, multiply 70 by 9.80665, which gives 686.4655 N. Swap in a different g — 1.62 for the Moon or 3.71 for Mars — and the same mass produces a smaller weight, because gravity there is weaker.
The result is a force, not a mass, which is the single most common point of confusion. Mass (kilograms) measures how much matter an object contains and stays the same everywhere in the universe; weight (newtons) measures the gravitational force on that matter and changes with location. Our 70 kg example weighs 686.4655 N on Earth, but the very same person would register about 113 N on the Moon and about 260 N on Mars — the mass is identical, only the pull differs. In everyday speech we say someone "weighs 70 kg", but strictly that 70 kg is their mass; their weight is the force in newtons. This distinction matters whenever forces are involved: a beam, a cable, or a foundation must be sized for the weight force it carries, and a spacecraft engineer must account for how much lighter a payload becomes once it leaves Earth.
The formula is exact, but a couple of practical points are worth keeping in mind.
Local gravity and consistent units
This calculator uses a single, constant value of g, so it assumes a uniform gravitational field. Real gravity varies slightly with latitude and altitude — it is a touch weaker at the equator and on a mountaintop than the standard 9.80665 m/s². Keep your units consistent: kilograms for mass and metres per second squared for gravity, otherwise the newtons will be wrong. The result is weight (a force), never mass; the two are equal in number only by coincidence of unit choice.