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Boyle's Law

Also known as P₁V₁ = P₂V₂ · pressure volume law

P1V1=P2V2P_1 V_1 = P_2 V_2
sig figs

Worked example: 2 L at 1 atm → 4 atm gives 0.5 L. Press Try an example to run it live, then adjust anything.

Enter your known values, leave one input blank, and solves for the missing one. Tap a variable’s symbol to see what it means, with a typical value. Change any unit and the answer follows.

Where Boyle's Law fits

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Gas Density from Molar MassPartial Pressure from Mole FractionCompressibility Factor (Z = PV/nRT)Gay-Lussac's Law
In this toolkit

See also

Combined Gas Law: Both use initial pressure and initial volume.Ideal Gas Law: Both use initial pressure and initial volume.Charles's Law: Both use initial volume.Compressibility Factor (Z = PV/nRT): Both use initial volume.Gas Volume at STP: Both use initial volume.Van der Waals Equation of State: Both use initial volume.
5 more relatedGay-Lussac's Law: Both use initial pressure.Cavitation Number (Margin above Vapour Pressure): Both use initial pressure.Dalton's Law of Partial Pressures: Both use initial pressure.Expansion Tank Acceptance Volume: Both use initial pressure.Gauge and Absolute Pressure: Both use initial pressure.
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Boyle's Law explained

P1V1P2V2

Robert Boyle published his gas law in 1662, making it one of the oldest quantitative laws in physics: at constant temperature, the pressure and volume of a trapped gas are inversely proportional, so their product never changes. Cap a syringe and squeeze: compress 60 mL of air at 100 kPa down to 20 mL and the pressure climbs to 300 kPa. Molecularly, shrinking the space raises how often molecules hammer the walls, and pressure rises in exact proportion.

The law matters wherever gas gets squeezed. Scuba divers learn it first: air breathed at depth expands as they ascend, which is why the cardinal rule is never to hold your breath on the way up. Boyle's law assumes the temperature and the amount of gas stay fixed; change either and you need Charles's law or the combined gas law instead.

Boyle's Law formula

P1V1=P2V2P_1 V_1 = P_2 V_2
Where
  • P1P_1= Initial pressure (kPa)
  • V1V_1= Initial volume (L)
  • P2P_2= Final pressure (kPa)
  • V2V_2= Final volume (L)
In this toolkit

The gas laws

5 formulasBoyle, Charles, Gay-Lussac, the combined law and the ideal gas law — each holding one property fixed, and how they collapse into PV = nRT.

Revised 30 October 2026
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formula.expert. (2026, October 30). Boyle's Law Formula & Calculator. https://formula.expert/solvers/boyles-law

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