Enter any three of the four variables — Initial Volume (V₁), Initial Temperature (T₁), Final Volume (V₂), or Final Temperature (T₂) — and the Charles' Law Calculator solves for the missing value, also giving you the Volume Ratio (V₂/V₁) and Temperature Ratio (T₂/T₁) so you can see exactly how your gas expands or contracts with temperature.
Calculated Value
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Unit
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Volume Ratio (V₂/V₁)
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Temperature Ratio (T₂/T₁)
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Charles' law states that the volume of a gas is directly proportional to its absolute temperature when pressure and amount of gas remain constant. Mathematically, V₁/T₁ = V₂/T₂.
Charles' law applies to hot air balloons (heated air expands and becomes less dense), tire pressure changes with temperature, and breathing (lung volume changes with body temperature).
To find final temperature T₂, rearrange the equation: T₂ = (V₂ × T₁) / V₁. Make sure all temperatures are in absolute units like Kelvin.
Charles' law only applies to ideal gases at constant pressure and amount. It breaks down at very high pressures or low temperatures where gases don't behave ideally.
Charles' law was discovered by Jacques Charles in the 1780s, though it was first published by Joseph Louis Gay-Lussac in 1802, who credited Charles with the discovery.
Temperature must be in absolute scale (Kelvin) because Charles' law involves ratios. Using Celsius or Fahrenheit would give incorrect results due to their arbitrary zero points.
According to Charles' law, when temperature increases at constant pressure, gas volume increases proportionally. This is because gas molecules move faster and occupy more space.