Calculates how a gas’s pressure and volume relate at constant temperature, using Boyle’s Law.
How it works
The product of initial pressure and volume equals the product of final pressure and volume, solved here for the final pressure.
What this does not include
This does not include temperature or the amount of gas changing — for the full pressure-volume-temperature relationship, use this site’s ideal gas law calculator instead.
How to use this calculator
- Enter the initial pressure and volume, and the final volume.
A worked example
A gas at pressure 1 atm and volume 2 L, compressed to 1 L: new pressure = (P1×V1)/V2 = (1×2)/1 = 2 atm — halving the volume doubles the pressure.
Pressure 2 atm, volume 3 L, expanded to 6 L: new pressure = 1 atm.
What the variables mean
| Variable | Meaning |
|---|---|
| P1, V1 | Initial pressure and volume |
| V2 | New volume |
Edge cases worth knowing
Pressure and volume move in opposite directions at constant temperature — compress the gas, pressure rises; expand it, pressure falls, exactly as both examples above show.
A final volume of zero makes the new pressure infinite, which has no physical meaning, so the calculator declines to show a result.
Frequently asked questions
Why does volume decrease as pressure increases?
At constant temperature, squeezing a gas into a smaller space forces its molecules closer together, which increases the pressure they exert — the two change in inverse proportion.
Does Boyle’s Law apply to any gas?
It’s an accurate approximation for ideal gases under typical conditions — real gases deviate somewhat at very high pressures or low temperatures.
What’s the difference between Boyle’s Law and the ideal gas law?
Boyle’s Law is the special case of the ideal gas law where temperature and the amount of gas are both held constant — the ideal gas law handles all four variables changing together.
