Gay-Lussac's Law Calculator
Enter any three of initial pressure, initial temperature, final pressure and final temperature, and this calculator finds the fourth using Gay-Lussac's Law, P1/T1 = P2/T2, at constant volume. Temperatures are converted to Kelvin for the math.
How to use the Gay-Lussac's Law calculator
- Pick which quantity you want to solve for.
- Choose Kelvin or Celsius and enter the other three values.
- Read the missing value, solved from P1/T1 = P2/T2.
Examples
Solve for final pressure
P1 = 1, T1 = 300 K, T2 = 600 K
P2 = 2
Solve for final temperature
P1 = 1, T1 = 300 K, P2 = 2
T2 = 600 K
Frequently asked questions
What is Gay-Lussac's Law?
Gay-Lussac's Law states that at constant volume the pressure of a fixed amount of gas is directly proportional to its absolute temperature, so P1/T1 = P2/T2.
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 pressure units can I use?
Any consistent unit works because only the ratio matters. Use the same unit for both P1 and P2.
How many values do I need to enter?
Exactly three of the four. From any three of P1, T1, P2 and T2 the fourth is fully determined.
How is this different from Boyle's and Charles's Law?
Gay-Lussac's Law holds volume constant and links pressure to temperature, while Boyle's holds temperature constant and Charles's holds pressure constant.
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