# Volume integral

In mathematics—in particular, in multivariable calculus—a **volume integral** refers to an integral over a 3-dimensional domain, that is, it is a special case of multiple integrals. Volume integrals are especially important in physics for many applications, for example, to calculate flux densities.

## In coordinatesEdit

It can also mean a triple integral within a region of a function and is usually written as:

A volume integral in cylindrical coordinates is

and a volume integral in spherical coordinates (using the ISO convention for angles with as the azimuth and measured from the polar axis (see more on conventions)) has the form

## Example 1Edit

Integrating the function over a unit cube yields the following result:

So the volume of the unit cube is 1 as expected. This is rather trivial however, and a volume integral is far more powerful. For instance if we have a scalar density function on the unit cube then the volume integral will give the total mass of the cube. For example for density function:

the total mass of the cube is:

## See alsoEdit

## External linksEdit

- Hazewinkel, Michiel, ed. (2001) [1994], "Multiple integral",
*Encyclopedia of Mathematics*, Springer Science+Business Media B.V. / Kluwer Academic Publishers, ISBN 978-1-55608-010-4 - Weisstein, Eric W. "Volume integral".
*MathWorld*.