About Charles' Law
Charles' Law describes how the volume of a gas changes with temperature when pressure and the amount of gas are held constant. First observed by French physicist Jacques Charles in the 1780s and published by Joseph Louis Gay-Lussac in 1802, it states that volume and absolute temperature are directly proportional: V₁/T₁ = V₂/T₂. This calculator uses your initial volume and temperature, plus a target final temperature, to find the resulting final volume.
Understanding the formula
Charles' Law falls out of the ideal gas law, PV = nRT. If pressure (P) and the number of moles (n) do not change, then V/T = nR/P is a constant, so V₁/T₁ must equal V₂/T₂. Rearranging for the unknown gives the final volume directly: V₂ = V₁ × (T₂ / T₁). Because the ratio only means something physical when temperature is measured from absolute zero, every temperature is converted to Kelvin before the calculation runs (K = °C + 273.15, or K = (°F − 32) × 5/9 + 273.15).
Working with temperature units
Enter your initial and final temperatures in Kelvin, Celsius, or Fahrenheit — the calculator converts whichever you pick into Kelvin internally, since Celsius and Fahrenheit both have zero points that are not physically meaningful for a gas's volume. Double-check that a "below zero" entry is still a valid physical state: 0 K (-273.15°C, -459.67°F) is absolute zero, and no real or ideal gas can exist below it, so the calculator rejects any temperature that converts to 0 K or less.
Knowing the limits
Charles' Law assumes an ideal gas at constant pressure and a fixed amount of gas — it does not apply if the gas is compressed, released, or allowed to escape, or if pressure changes during the process (use the combined gas law, P₁V₁/T₁ = P₂V₂/T₂, instead). It is a good approximation for common gases like air, oxygen, or nitrogen at everyday temperatures and pressures — think of a balloon shrinking in cold air or a bicycle tire's pressure rising as it warms in the sun. Near a gas's condensation point or at very high pressure, real-gas effects make the ideal relationship less accurate.
Frequently Asked Questions
What is Charles' Law?
Why does the temperature need to be in Kelvin?
What has to stay constant for Charles' Law to apply?
Does Charles' Law work for real gases?
Common Tip Percentages
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General Household Budget Ratios (50/30/20 Rule)
| Category | % of Net Income | Examples |
|---|---|---|
| Needs | 50% | Rent, groceries, utilities, insurance |
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Common Measurement Conversions for Everyday Use
| Quantity | US / Imperial | Metric Equivalent |
|---|---|---|
| 1 cup | 8 fl oz | 237 mL |
| 1 pint | 16 fl oz | 473 mL |
| 1 quart | 32 fl oz | 946 mL |
| 1 gallon | 128 fl oz | 3.785 L |
| 1 lb | 16 oz | 453.6 g |
| 1 ft | 12 in | 30.48 cm |