Calculator
Choose one variable to solve. Enter the remaining three values with their units. If you use gauge pressure, the calculator converts to absolute pressure first.
Example Data Table
| Case | P₁ | V₁ | P₂ | V₂ | What Happens |
|---|---|---|---|---|---|
| Example 1 | 1 atm | 2 L | 2 atm | 1 L | Halving volume doubles pressure. |
| Example 2 | 100 kPa | 3 L | 150 kPa | 2 L | Compression increases pressure inversely. |
| Example 3 | 14.7 psi | 0.50 ft³ | 29.4 psi | 0.25 ft³ | Pressure doubles when volume halves. |
| Example 4 | 760 mmHg | 500 mL | 380 mmHg | 1000 mL | Doubling volume halves pressure. |
Formula Used
P₁ = (P₂ × V₂) / V₁
V₁ = (P₂ × V₂) / P₁
P₂ = (P₁ × V₁) / V₂
V₂ = (P₁ × V₁) / P₂
This calculator assumes:
- Temperature remains constant.
- The amount of gas remains constant.
- Pressure must be absolute for the law itself.
- All unit conversions are handled before solving.
How to Use This Calculator
- Select the variable you want to solve.
- Choose whether pressure entries are absolute or gauge values.
- Enter atmospheric pressure if gauge mode is selected.
- Type the other three known values and choose their units.
- Pick your preferred significant figures and graph density.
- Press the calculate button.
- Review the solved value, steps, summary table, and graph.
- Use the CSV or PDF buttons to export the result.
Frequently Asked Questions
1) What does Boyle’s law describe?
Boyle’s law describes the inverse relationship between pressure and volume for a fixed amount of gas at constant temperature. When volume decreases, pressure increases proportionally, and vice versa.
2) Why should pressure be absolute?
Gas laws use absolute pressure because zero must represent a true physical zero. Gauge pressure ignores atmospheric pressure, so this calculator converts gauge inputs to absolute values before solving.
3) Can I use different units for each input?
Yes. You can mix pressure and volume units freely. The calculator converts everything internally to SI units, solves the equation, and then returns the result in your selected unit.
4) When does Boyle’s law fail?
It becomes less accurate when temperature changes, gas leaks occur, or real-gas effects become important at very high pressures or very low temperatures.
5) What is the Boyle constant shown in results?
It is the constant product P × V for the gas state under the stated assumptions. The calculator shows it in Pa·m³ to verify that both sides of the equation match.
6) What does the graph show?
The graph plots the isothermal pressure–volume curve for the computed gas constant. It also marks the initial and final states so you can see how compression or expansion changes pressure.
7) Can this calculator solve any one variable?
Yes. You can solve for initial pressure, initial volume, final pressure, or final volume. Provide the other three values and make sure they are physically valid.
8) Is this useful for chemistry labs and homework?
Yes. It helps with unit conversion, step-by-step checks, state summaries, and printable exports, making it practical for classwork, reports, and experiment preparation.