Combined Gas Law Calculator
Enter any five of initial and final pressure, volume and temperature, and this calculator finds the sixth using the combined gas law, P1V1/T1 = P2V2/T2. Temperatures are converted to Kelvin for the math.
How to use the combined gas law calculator
- Pick which quantity you want to solve for.
- Choose Kelvin or Celsius and enter the other five values.
- Read the missing value, solved from P1V1/T1 = P2V2/T2.
Examples
Solve for final temperature
P1 = 1, V1 = 2, T1 = 300 K, P2 = 2, V2 = 1
T2 = 300 K
Solve for final volume
P1 = 1, V1 = 1, T1 = 273.15 K, P2 = 2, T2 = 546.3 K
V2 = 1
Frequently asked questions
What is the combined gas law?
The combined gas law merges Boyle's, Charles's and Gay-Lussac's laws into P1V1/T1 = P2V2/T2 for a fixed amount of gas.
Why must temperature be in Kelvin?
The law only holds on an absolute scale. Celsius values are converted by adding 273.15 to get Kelvin before solving, then converted back.
What units can I use for pressure and volume?
Any consistent units work because only the ratios matter. Use the same unit for both pressures and the same unit for both volumes.
How many values do I need to enter?
Exactly five of the six. From any five of P1, V1, T1, P2, V2 and T2 the sixth is fully determined.
How does it relate to the ideal gas law?
The combined gas law compares two states of the same gas, while the ideal gas law PV = nRT also brings in the amount of gas in moles.
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