Science & engineering · Gas laws
Charles's law calculator.
Solve the missing volume or temperature of a gas at constant pressure.
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How does Charles's Law work?
Charles's law: the volume of a gas is directly proportional to its absolute temperature, so V1 / T1 = V2 / T2. It holds for a fixed amount of gas at constant pressure. Temperatures must be on an absolute (kelvin) scale: add 273.15 to Celsius, which this tool does for you.
Worked example. 0.300 L of gas at 283 K is warmed to 303 K at constant pressure. V2 = 0.300 x 303 / 283 = 0.321 L (OpenStax Example 9.6).
Pressure and volume must be in the same unit on both sides of the equation, and the answer comes back in that unit. Temperatures are converted to kelvin internally, as the source requires.
Frequently asked questions
What is Charles's law?
At constant pressure, the volume of a fixed amount of gas is proportional to its temperature on the kelvin scale: V1/T1 = V2/T2.
Why must temperature be in kelvin?
The proportionality is to absolute temperature. Using Celsius directly would give wrong answers, so this tool converts Celsius and Fahrenheit to kelvin first.
What if I enter 0 K or a negative kelvin value?
The tool rejects it: temperature must be above absolute zero.
Is the volume unit important?
Use the same unit for V1 and V2. The answer is returned in that unit.
Sources
Checked
Formulas and the worked example are from the source above. Runs entirely in your browser. Nothing you type is sent or stored.
Scope
Education and general engineering reference only. These laws assume an ideal gas at constant amount and the held-constant quantity named on this page; real gases at high pressure or low temperature deviate. Not a substitute for a safety calculation on pressure vessels or compressed gas equipment.