Combined Gas Law Calculator
Combined gas law calculator (P1V1/T1 = P2V2/T2): find the new pressure, volume or temperature of a fixed amount of gas.
P1 · V1T1 = P2 · V2T2
How to use this calculator
- Choose the quantity you want under “Solve for”.
- Type the known values and pick their units: any combination works.
- The result updates as you type. Open “Show the steps” to see the substitution.
For a fixed amount of gas, P·V/T stays constant, so P1V1/T1 = P2V2/T2. It combines Boyle’s, Charles’s and Gay-Lussac’s laws.
To use Boyle’s law, set T₁ = T₂; for Charles’s law set P₁ = P₂. Temperatures are converted to kelvin before calculating.
Formula
P1 · V1T1 = P2 · V2T2
| Symbol | Quantity | Units |
|---|---|---|
| P1 | Initial pressure | Pa, kPa, MPa, hPa, bar, mbar, atm, Torr, mmHg, psi, inHg |
| V1 | Initial volume | L, mL, µL, m³, dm³, cm³, gal, gal (UK), qt, pt, cup, fl oz, ft³, in³ |
| T1 | Initial temperature | K, °C, °F, °R |
| P2 | Final pressure | Pa, kPa, MPa, hPa, bar, mbar, atm, Torr, mmHg, psi, inHg |
| T2 | Final temperature | K, °C, °F, °R |
| V2 | Final volume | L, mL, µL, m³, dm³, cm³, gal, gal (UK), qt, pt, cup, fl oz, ft³, in³ |
Worked example
Given: P1 = 1 atm · V1 = 2 L · T1 = 25 °C · P2 = 2 atm · T2 = 75 °C
V2 = P1 · V1 · T2T1 · P2
Result: V2 = 1.1677 L
Frequently asked questions
How do I use it as Boyle’s law?
Enter the same temperature for T₁ and T₂. Then P₁V₁ = P₂V₂.
Why do I get a wrong answer when I use °C by hand?
Gas laws need absolute temperature. 25 °C → 50 °C does not double the volume; 298.15 K → 323.15 K raises it by only 8.4 %.