Dalton's law states that the total pressure of a mixture of gases is equal to the sum of the partial pressures of the component gases. Use this online Dalton's law of partial pressure calculator to estimate the total pressure of the mixture of gases using Dalton's law. There is no one specific pressure unit you have to use when doing problems with Dalton's partial-pressures equation. Calculate the partial pressure of combined gas with known values of temperature and mole of gas.