What is the difference between mass and weight?
Mass is the amount of matter in an object and stays the same everywhere. Weight is the force of gravity pulling on that mass, so it changes depending on where you are.
Mass is measured in kilograms or grams. An object's mass does not change whether it is on Earth, on the Moon or floating in space. Weight is a force, measured scientifically in newtons. It is calculated by multiplying mass by the strength of gravity. On Earth, gravity gives about 9.8 newtons of weight for every kilogram of mass.
On the Moon, gravity is about one-sixth as strong as on Earth. An astronaut with a mass of 80 kilograms would still have a mass of 80 kilograms there, but would weigh only about one-sixth as much. On Jupiter, the same astronaut would weigh about two and a half times as much as on Earth.
Everyday language
In everyday life, people use weight to mean mass, such as saying a bag of flour weighs one kilogram. Bathroom scales actually measure the force you press down with and then convert it into kilograms or pounds, assuming Earth's gravity.
Did You Know?
You weigh very slightly less at the equator than at the poles, because Earth's spin and shape reduce the effective pull of gravity there.