A partial pressure equation can be solved in more than one way. The total pressure is the sum of the partial pressures as shown in the following equation: Ptot = P1 + P2 + P3. If the components of a pressure are given, you may calculate the partial pressures and add them to find the total pressure. These pressures can be found through the following equation: p = nRT/V.

**Determine the equation needed**Review the given information to determine which method needs to be used. If you are given a total pressure and one or more partial pressures, you may be able to simply subtract the partial pressures from the total pressure to find your solution.

**Calculate the partial pressure from the given information**Calculate the partial pressure from the information supplied to you in the problem and the aforementioned equation. The symbol "V" is equal to the volume, "T" is temperature, "n" is the number of moles and "R" is the gas constant, for which a value of 0.0821 is used. In some cases, the mass of a gas may be used in place of the number of moles.

**Calculate the answer and convert**Using the equation of partial pressures, insert the values and calculate the answer. For the gas constant, the units are liters, atmospheres, moles and Kelvins in the following relationship: L x Atm/mol x K. If the givens vary, apply the appropriate conversions to get the correct answer.