Squeeze a gas into half the volume and its pressure doubles – as long as the temperature stays the same. Robert Boyle discovered this in 1662; it explains syringes, breathing and why divers’ lungs must equalise.
How to use the Boyle’s Law Calculator
- Find
- Initial pressure p₁
- Initial volume V₁
- Final volume V₂
- Final pressure p₂
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 other three 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 pressure p₂, Final volume V₂ |
| Initial pressure p₁ | Units: kPa, Pa, bar, atm, psi, MPa |
| Initial volume V₁ | Units: L, m³, mL, ft³ |
| Final volume V₂ | Units: L, m³, mL, ft³ |
| Final pressure p₂ | Units: kPa, Pa, bar, atm, psi, MPa |
What each result means
- Final pressure p₂ = [Initial pressure p₁]×[Initial volume V₁]÷[Final volume V₂]
- Final volume V₂ = [Initial pressure p₁]×[Initial volume V₁]÷[Final pressure p₂]
Example values
How the main result changes when Initial pressure p₁ changes and everything else stays at the example values above:
| Initial pressure p₁ (kPa) | Final pressure p₂ (kPa) |
|---|---|
| 50.66 | 101.325 |
| 75.99 | 151.9875 |
| 101.33 | 202.65 |
| 126.66 | 253.3125 |
| 151.99 | 303.975 |
| 202.65 | 405.3 |
Formula
p₁·V₁ = p₂·V₂Worked example
Inputs — Find: Final pressure p₂; Initial pressure p₁: 101.325 kPa; Initial volume V₁: 10 L; Final volume V₂: 5 L.
Results — Final pressure p₂ = 202.65 kPa.
Key terms
- Isothermal
- At constant temperature.
Frequently asked questions
Does Boyle's law need constant temperature?
Yes – it describes isothermal changes.
Why do bubbles grow as they rise in water?
Pressure decreases, so their volume increases.
Are pressures absolute?
Yes – use absolute, not gauge, pressure.
Does it apply to real gases?
Well at low pressures; deviations appear at high pressures.
What formula does the Boyle's Law Calculator use?
p₁·V₁ = p₂·V₂.