# What Is the Difference Between Mass and Weight?

(Last Updated On: August 8, 2018) For many, “mass” and “weight” are used interchangeably to refer to the size or heft of an object. However, these two words have different meanings and have their own respective units of measurement. So, what is the difference between mass and weight?

Generally speaking, mass refers to the amount of matter an object contains. Weight, on the other hand, is determined by how much gravity is exuded upon the object. Let’s explore these differences a bit more.

## What Is the Difference Between Mass and Weight?

While on Earth, mass and weight will have the same value (if you happen to be standing in a location where the force of gravity is 1G). However, if you were to relocate to an area where there was a gravitational shift, your mass would stay the same while your weight would change.

Generally, an object will either remain in one spot or, with some force given, move continuously in a straight line until it encounters another type of force. Think of a rolling ball hitting a wall.  Mass is a measure of how much force it takes for the object to change its path. It measures an object’s tendency to resist changing its state of motion, which is referred to as inertia.

Weight increases with the object’s mass. The more inertia an object has, the harder gravity will pull on it. This has a direct effect on its weight, which will increase or decrease depending on the state of gravity at the object’s location. For example, on the surface of the Moon (where gravity is weaker) an object will weigh less than it would on Earth, where gravity is stronger.

## What Is Matter?

Mass is dependent on how much matter there is in an object. More mass means more inertia, since there is more of an object that needs to be taken into consideration for movement.

What exactly is matter? Matter is anything that has mass and occupies space. Matter makes up atoms and compounds, which build the things you interact with every day.

This matter can be solid, liquid or gas. The size of an object does not directly affect its mass. For example, you could have a large object filled with comparatively less mass (such as a beach ball filled with air) or a small object that contains a great deal of mass (like a metal statue).

## Measuring Mass vs. Weight

In the United States, scales measure weight in pounds. In nearly every other country in the world, weight is measured in metric units like grams or kilograms. Mass is also measured in kilograms.

Technically, weight should be measured in newtons, which are the units of force. However, this isn’t a commonly used measurement outside of the scientific world. Weight measures how much downward force gravity applies to a given object. On Earth, this force of gravity is approximately 9.8 newtons per kilogram.

While mass can never be zero, it’s possible for an object to be weightless. This occurs when there is no gravity to press down upon an object and give it weight, such as in space.