Science & engineering · Gas laws
Boyle's law calculator.
Solve the missing pressure or volume of a gas at constant temperature.
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Leave exactly one box empty.
How does Boyle's Law work?
Boyle's law: the volume of a gas is inversely proportional to its pressure, so P1 x V1 = P2 x V2. It holds for a fixed amount of gas at constant temperature. Temperatures must be on an absolute (kelvin) scale: add 273.15 to Celsius, which this tool does for you.
Worked example. A gas at 13.0 psi in 15.0 mL is compressed to 7.5 mL. Then P2 = 13.0 x 15.0 / 7.5 = 26 psi (OpenStax Example 9.8).
Pressure and volume must be in the same unit on both sides of the equation, and the answer comes back in that unit. Temperatures are converted to kelvin internally, as the source requires.
Frequently asked questions
What is Boyle's law?
For a fixed amount of gas at constant temperature, pressure times volume stays constant: P1V1 = P2V2. Halving the volume doubles the pressure.
Do I need to convert units for Boyle's law?
Only that both pressures share one unit and both volumes share one unit. The ratio cancels the unit, so you do not need to convert to pascals or litres.
Does temperature have to be in kelvin?
Temperature does not appear in Boyle's law, but the law only holds if the temperature stays constant. For problems where temperature changes use the combined gas law.
Can I solve for volume or for the first pressure?
Yes. Leave any single box empty and the calculator solves for it.
Sources
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Formulas and the worked example are from the source above. Runs entirely in your browser. Nothing you type is sent or stored.
Scope
Education and general engineering reference only. These laws assume an ideal gas at constant amount and the held-constant quantity named on this page; real gases at high pressure or low temperature deviate. Not a substitute for a safety calculation on pressure vessels or compressed gas equipment.