Boyle's law also referred to as the Boyle-Mariotte Law is one among the several gas laws and a special case of the ideal gas law. The law was named after chemist and physicist Robert Boyle. The law states that the volume of a gas increases when the pressure decreases at a constant temperature. This Boyle's law calculator can calculate the pressure and volume change of gas if you provide 3 out of the 4 variables in the Boyle-Mariotte’s equation where the temperature (t) is constant.