# What is the difference between mass and weight?

Mass is a fundamental measure of the amount of matter contained in an object. Weight is a measure of the gravitational force on an object. It not only depends on the mass of the object, but also on its location. Therefore, weight is actually a measure of strength.

Mass depends on the amount of matter (atoms, etc.) in an object; more mass means more inertia, since there is more to move. This is Isaac Newton's idea of mass, which underpins his famous laws of motion developed in the late 17th century. It's not entirely accurate at extremely high speeds, where Albert Einstein's 20th-century special theory of relativity is required, but it's OK for most everyday situations. Federal law, which replaces this manual, also defines the peso, in particular the net weight, in terms of the avoirdupolis pound or massive pound.

The use of the term mass predominates around the world and is becoming increasingly common in the United States. While a person's mass doesn't change anywhere in the solar system, acceleration due to gravity and weight varies dramatically. In scientific contexts, mass is the amount of matter in an object (although matter can be difficult to define), but weight is the force exerted on the matter of an object by gravity. Since objects with exactly the same mass but with different densities displace different volumes and therefore have different floats and weights, any object measured on this scale (compared to a standard stainless steel mass) measures its conventional mass, that is, its true mass minus an unknown degree of buoyancy.

Of course, you would die in the Sun from massive heat and other radiation, but even if it were cold, the intense gravity of a planet of that size would be deadly. In the International System of Units (SI), the kilogram is the basic unit of mass and the newton is the basic unit of force. The weight of the object is lower on Mars, where gravity is weaker; more on Saturn, where gravity is stronger; and very small in space, far from important sources of gravity, but it always has the same mass. The net mass or net weight stated on a label indicates that the package contains a specific quantity of product, not including packaging materials.

In the physical sciences, the terms mass and weight are rigidly defined as separate measures, since they are different physical properties. Engineers in disciplines related to weight load (force on a structure due to gravity), such as structural engineering, convert the mass of objects such as concrete and cars (expressed in kilograms) into a force in newtons (multiplying by some factor of around 9.8; 2 significant figures are usually sufficient for such calculations) to deduce the object's load. Your mass is the same no matter where in the universe you go; your weight, on the other hand, changes from place to place. Although the rubber that makes up the balloon has a mass of only a few grams, which can be almost imperceptible, the rubber still retains all its mass when inflated.

In general, the relationship between mass and weight on Earth is highly proportional; objects that are a hundred times more massive than a one-liter bottle of soda almost always weigh a hundred times more, approximately 1000 newtons, which is the weight you would expect on Earth from an object with a mass slightly greater than 100 kilograms. In common usage, the mass of an object is often referred to as its weight, although in reality these are different concepts and quantities.