Gases expand when heated: at constant pressure, volume is proportional to absolute temperature. Hot-air balloons rise because the heated air expands and becomes less dense.
How to use the Charles’s Law Calculator
- Find
- Initial volume V₁
- Initial temperature T₁
- Final temperature T₂
- Final volume V₂
Results update as you type, every field has its own unit menu, and everything is calculated in your browser.
How it works
Choose what to find and enter the known values.
Tips
- Use absolute temperature (K) in gas laws and efficiency formulas.
- Temperature differences are the same in K and °C.
- Heat = mass × specific heat × temperature change when no phase change occurs.
- Phase changes need latent heat at a constant temperature.
Common mistakes to avoid
- Using °C in pV = nRT.
- Forgetting latent heat during melting or boiling.
- Confusing heat capacity (J/K) with specific heat (J/(kg·K)).
Inputs explained
| Field | What to enter |
|---|---|
| Find | Choose one: Final volume V₂, Final temperature T₂ |
| Initial volume V₁ | Units: L, m³, mL, ft³ |
| Initial temperature T₁ | Units: K, °C, °F |
| Final temperature T₂ | Units: K, °C, °F |
| Final volume V₂ | Units: L, m³, mL, ft³ |
What each result means
- Final volume V₂ = [Initial volume V₁]×[Final temperature T₂]÷[Initial temperature T₁]
- Final temperature T₂ = [Initial temperature T₁]×[Final volume V₂]÷[Initial volume V₁]
Example values
How the main result changes when Initial volume V₁ changes and everything else stays at the example values above:
| Initial volume V₁ (L) | Final volume V₂ (L) |
|---|---|
| 0.5 | 0.6364 |
| 0.75 | 0.9547 |
| 1 | 1.2729 |
| 1.25 | 1.5911 |
| 1.5 | 1.9093 |
| 2 | 2.5458 |
Formula
V₁/T₁ = V₂/T₂ (absolute temperatures)Worked example
Inputs — Find: Final volume V₂; Initial volume V₁: 1 L; Initial temperature T₁: 293.15 K; Final temperature T₂: 373.15 K.
Results — Final volume V₂ = 1.2729 L.
Key terms
- Isobaric
- At constant pressure.
Frequently asked questions
Why must temperatures be absolute?
Volume is proportional to kelvin temperature, not Celsius.
What happens at absolute zero?
An ideal gas would have zero volume – real gases liquefy first.
How much does air expand from 20 °C to 100 °C?
About 27%.
Who discovered it?
Jacques Charles (~1787), published by Gay-Lussac in 1802.
What formula does the Charles's Law Calculator use?
V₁/T₁ = V₂/T₂ (absolute temperatures).