Find the number of moles of gas from pressure, volume and temperature.
The ideal gas law, PV = nRT, ties together the pressure, volume, temperature, and amount of a gas. Here R is the universal gas constant, 8.314 J/(mol·K), and n is the number of moles. The law treats gas molecules as point particles with no interactions, which is a good approximation for real gases at low pressure and high temperature.
Enter the pressure in pascals, the volume in cubic metres, and the absolute temperature in kelvin. The calculator returns the number of moles and also converts the pressure to atmospheres (1 atm = 101 325 Pa). At standard conditions, one mole of gas occupies about 22.4 litres.
The gas law is built on absolute temperature. Using Celsius would give wrong, even negative, results. Add 273.15 to convert from Celsius to kelvin.
At high pressures or low temperatures, where molecules are close together and intermolecular forces matter, real gases deviate from ideal behaviour.