Combined Gas Law Calculator
Combined gas law calculator: solve for the final pressure, volume or temperature using P1V1/T1 = P2V2/T2.
Editorial review: Farrow (pseudonym; identity and professional credentials are not disclosed). This page is for educational purposes, not professional advice.
Your inputs
Results update as you type. Nothing you enter leaves your device.
Results
Example with the starting values
These results use the calculator's initial inputs. Change the values above to calculate your own estimate.
Inputs
- Solve for
- Final volume (V2)
- Initial pressure (P1)
- 1 atm
- Initial volume (V1)
- 2 L
- Initial temperature (T1)
- 300 K
- Final pressure (P2)
- 1 atm
- Final volume (V2)
- 4 L
- Final temperature (T2)
- 600 K
Results
- Final volume (V2)
- 4 L
How does the Combined Gas Law Calculator work?
The combined gas law is P1·V1 / T1 = P2·V2 / T2 for a fixed amount of gas. Temperature must be in kelvin.
For example, 1 atm, 2 L at 300 K heated to 600 K at 1 atm gives V2 = 1 × 2 × 600 ÷ (300 × 1) = 4 L.
Frequently asked questions
What happens if pressure stays constant?
The law reduces to Charles's law, V1/T1 = V2/T2. If temperature is constant, it reduces to Boyle's law.
What is the combined gas law?
P1V1/T1 = P2V2/T2. It merges Boyle's, Charles's and Gay-Lussac's laws for a fixed amount of gas.
Why use kelvin?
The law needs absolute temperature. Convert °C to K by adding 273.15.
Do the pressure and volume units matter?
Only that each pair matches: P1 and P2 in one unit, V1 and V2 in one unit.
Related calculators
Practice it: Gas Piston, a free gas law game.
Practice it: Thermo Tune, a free fahrenheit to celsius game.