Charles’s Law Calculator
Calculate the final volume of a gas at constant pressure using Charles’s law (V₁/T₁ = V₂/T₂).
How it works
- 1Enter the initial volume V₁ in litres, then the initial temperature T₁ and target final temperature T₂. Switch °C (metric) and °F (imperial) with the toggle.
- 2Temperatures are converted to kelvin first — Charles’s law needs absolute temperatures: T(K) = T(°C) + 273.15.
- 3The calculator applies V₂ = V₁·T₂ ÷ T₁ and shows the final volume with the absolute temperatures used.
Use cases
- Predicting how a balloon or sealed container’s volume changes when heated or cooled at constant pressure.
- Lab work — checking gas-volume readings against the Charles’s-law prediction.
- HVAC — estimating duct-air volume change across a temperature difference at constant pressure.
Frequently asked questions
What is Charles’s law?
For a fixed amount of gas at constant pressure, volume is directly proportional to absolute temperature: V₁/T₁ = V₂/T₂, so V₂ = V₁·T₂ ÷ T₁.
Why must temperature be in kelvin?
Charles’s law is a ratio of absolute temperatures. In °C, 0° would falsely imply zero volume. Kelvin starts at absolute zero, so V/T is always meaningful. The tool converts °C/°F to kelvin automatically.
Can you show a worked example?
A gas occupies 2 L at 300 K and is heated to 600 K at constant pressure: V₂ = 2 × 600 ÷ 300 = 4 L. Doubling the absolute temperature doubles the volume.
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