Charles's Law Calculator
Use Charles's law to find the new volume of a gas when its temperature changes at constant pressure.
How it works
V₁ / T₁ = V₂ / T₂ · V₂ = V₁ × T₂ / T₁
Charles's law states that at constant pressure the volume of a fixed amount of gas is directly proportional to its absolute temperature. Double the kelvin temperature and the gas takes up twice the space. The ratio V/T stays constant, so the new volume scales with the temperature ratio.
Worked example
A 10 L gas warmed from 300 K to 350 K expands to V₂ = 10 × 350 ÷ 300 ≈ 11.67 L.
Frequently asked questions
Why does temperature have to be in kelvin?
Volume is proportional to absolute temperature. Only the kelvin scale starts at absolute zero, so Celsius would give wrong ratios and could even produce negative volumes.
What is held constant here?
Pressure and the amount of gas are fixed. Charles’s law describes how volume responds to temperature alone.
Is this why balloons shrink in the cold?
Yes. Cooling a balloon lowers the absolute temperature, so the gas contracts and the balloon visibly deflates, then re-expands when it warms up.
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Educational estimate. Check the formula and units for your exact case.