Charles's Law Calculator — Volume and Temperature of a Gas
Charles's Law states that the volume of a fixed amount of gas is directly proportional to its absolute temperature at constant pressure. Enter the initial volume, initial temperature, and either the final temperature (to find V₂) or the final volume (to find T₂).
Solve for
L
°C
°C
T₁ = 298.15 K → T₂ = 373.15 K
Convert temperatures to Kelvin
Apply Charles's Law: V₁/T₁ = V₂/T₂
Solve for V₂ = V₁ × T₂ / T₁
- 1
Convert T₁ to Kelvin
T₁ = 25 + 273.15 = 298.15 - 2
Convert T₂ to Kelvin
T₂ = 100 + 273.15 = 373.15 - 3
Final volume V₂
V₂ = 2 × 373.15 ÷ 298.15 = 2.5031V₂ = V₁ × T₂/T₁ — volume scales proportionally with absolute temperature.
How does this calculator work?
Charles's Law: V₁/T₁ = V₂/T₂ (T in Kelvin). At constant pressure, gas volume is directly proportional to absolute temperature. Double the Kelvin temperature → double the volume. To convert: K = °C + 273.15. Solve for V₂ = V₁ × T₂/T₁ or T₂ = T₁ × V₂/V₁.
Formula
How this is calculated
Charles's Law was formulated by Jacques Charles in 1787 and formalised by Gay-Lussac in 1802. It describes one of the three classic ideal-gas relationships: at constant pressure and with a fixed amount of gas, volume and absolute temperature are directly proportional — doubling the Kelvin temperature doubles the volume. The law is a special case of the Ideal Gas Law (PV = nRT) with P and n held constant, so V/T = nR/P = constant.
The key requirement is that temperature must be expressed in Kelvin (absolute temperature), not Celsius or Fahrenheit. At 0 K the volume would theoretically shrink to zero, but in practice real gases liquefy before that point. The formula V₁/T₁ = V₂/T₂ can be rearranged to solve for any one unknown given the other three: V₂ = V₁ × T₂/T₁, or T₂ = T₁ × V₂/V₁.
This calculator assumes ideal-gas behaviour, constant pressure, and a closed system (constant amount of gas). Real gases deviate from ideal behaviour at high pressures and low temperatures; for those conditions the van der Waals equation is more appropriate. The Kelvin conversion (°C + 273.15) is applied automatically.
Frequently asked questions
Kelvin is the absolute temperature scale starting at 0 K (absolute zero, −273.15 °C). Charles's Law says V ∝ T, which is only valid on an absolute scale. Using Celsius or Fahrenheit would give a non-zero offset and break the direct proportionality. At 0 °C (273.15 K) a gas still has volume; at 0 K it would theoretically have none.
Boyle's Law relates pressure and volume at constant temperature (PV = constant), while Charles's Law relates volume and temperature at constant pressure (V/T = constant). The third classic relationship is Gay-Lussac's Law (P/T = constant at constant volume). Together they combine into the Ideal Gas Law PV = nRT.
No. Charles's Law applies only to gases. Liquids and solids do expand with temperature (thermal expansion), but the relationship is much weaker and non-linear, described by volumetric expansion coefficients rather than the gas law. Above a gas's critical temperature and pressure the distinction between liquid and gas breaks down (supercritical fluid).
TG we-Calculate Editorial Team. (2026). Charles's Law Calculator — Volume and Temperature of a Gas [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/charles-law-calculator
TG we-Calculate Editorial Team. "Charles's Law Calculator — Volume and Temperature of a Gas." TG we-Calculate. 2026. https://we-calculate.com/calculator/charles-law-calculator.
TG we-Calculate Editorial Team, "Charles's Law Calculator — Volume and Temperature of a Gas," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/charles-law-calculator
@misc{wecalculate_charles_law_calculator, title = {Charles's Law Calculator — Volume and Temperature of a Gas}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/charles-law-calculator}}, year = {2026}, note = {TG we-Calculate} }
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