The gas laws are physical laws concerning the behavior of gases. They include Boyle’s law, which states that the volume of a given mass of gas at a constant temperature is inversely proportional to its pressure; and Charles’s law, which states that the volume of a given mass of gas at constant pressure is directly proportional to its absolute temperature. These two laws can be combined to give the General or Universal gas law, which may be expressed as:

Avogadro’s law states that equal volumes of all gases contain the same number of particles if they all have the same pressure and temperature.

The laws are not obeyed exactly by any real gas, but many common gases obey them under certain conditions, particularly at high temperatures and low pressures.