Boyle's Law Calculator
Use Boyle's law to find the new volume of a gas when its pressure changes at constant temperature.
How it works
P₁V₁ = P₂V₂ · V₂ = P₁V₁ / P₂
Boyle's law says that at constant temperature the pressure of a fixed amount of gas is inversely proportional to its volume: squeeze it into half the space and the pressure doubles. The product P × V stays constant, so the new volume is the old pressure-volume product divided by the new pressure.
Worked example
A gas at 1 atm filling 10 L is compressed to 2 atm. V₂ = (1 × 10) ÷ 2 = 5 L, exactly half the original volume.
Frequently asked questions
What stays constant in Boyle’s law?
Temperature and the amount of gas are held fixed. Only pressure and volume change, and they do so in inverse proportion.
Does the pressure unit matter?
No, as long as both pressures use the same unit. The units cancel in the ratio, so atmospheres, kilopascals or mmHg all give the same volume answer.
What if the temperature also changes?
Then Boyle’s law alone is not enough. Use the combined gas law or the full ideal gas law, which account for temperature changes as well.
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