# Boyle's law

**Boyle's Law** is one of the

gas laws, and relates the

volume and

pressure of an

ideal gas held at a constant

temperature.

The law, expressed in symbols, is:

*PV* = *k*

Where

*V* is the

volume of gas,

*P* is its

pressure, and

*k* is a constant. The volume is expressed in cubic metres or litres and the pressure in pascals when using

SI units.

To maintain the constant during an increase in pressure of a gas, at fixed temperature, requires that the volume decrease. Conversely, reducing the pressure of the gas increases the volume.

The exact value of the constant need not be known to make use of the law in comparison between two volumes of gas at equal temperature:

*P*_{1}*V*_{1} = *P*_{2}*V*_{2}

Together with the

Law of Charles and Gay-Lussac and

Graham's law, Boyle's law forms

gas laws, which describes the behaviour of an

ideal gas. The three gas laws can be generalized by the

universal gas equation.