About this calculator
Enter temperatures in °C if you like; they are converted to kelvin before calculating, which is the step most often missed.
How to use it
- Choose what to find, enter the other values with their units, and read the answer in every common unit.
The formula
V₁ ÷ T₁ = V₂ ÷ T₂, T in kelvin
- T
- absolute temperature: °C + 273.15
Worked example
2 L at 27 °C heated to 127 °C
- T₁ = 300.15 K, T₂ = 400.15 K.
- V₂ = 2 × 400.15 ÷ 300.15 = 2.67 L.
What the result means
Doubling the Celsius temperature does not double the volume; doubling the kelvin temperature does.
Assumptions
- Constant pressure and amount of gas.
Limitations
- Ideal gas behaviour.
Frequently asked questions
Why use kelvin?
Volume is proportional to absolute temperature, which starts at absolute zero.
What is absolute zero?
0 K, or −273.15 °C.
What is Gay-Lussac’s law?
The pressure version: P₁/T₁ = P₂/T₂ at constant volume.
Last reviewed on 6 October 2026. Found a mistake? Tell us.