Boyle's Law Calculator

Last updated: June 2026

Find

Initial pressure P1

same units

Initial volume V1

same units

Final pressure P2

same units

Final volume V2

Formula

Boyle's law: P1 x V1 = P2 x V2 at constant temperature. Rearrange to V2 = P1 x V1 / P2 or P2 = P1 x V1 / V2.

Boyle's law pattern

Change	Effect
Pressure doubles	Volume halves
Pressure halves	Volume doubles
Temperature changes	Use a gas law with temperature instead

About this calculator

The Boyle's Law Calculator solves final pressure or final volume when temperature and amount of gas stay constant. It is useful for simple gas-compression examples, classroom chemistry questions, and understanding inverse pressure-volume relationships.

Boyle's law

Boyle's law says pressure multiplied by volume stays constant for a fixed amount of gas at constant temperature.

P1 x V1 = P2 x V2
V2 = P1 x V1 / P2
P2 = P1 x V1 / V2

How to use the Boyle's law calculator

Choose whether you want final pressure or final volume.
Enter initial pressure and initial volume.
Enter the known final pressure or final volume.
Keep pressure units consistent with each other.
Keep volume units consistent with each other.
Review the inverse relationship shown in the result.

Worked examples

Compressed gas

Input: P1 = 1 atm, V1 = 10 L, P2 = 2 atm

Calculation: V2 = 1 x 10 / 2

Result: 5 L

Expanded gas

Input: P1 = 100 kPa, V1 = 2 L, V2 = 4 L

Calculation: P2 = 100 x 2 / 4

Result: 50 kPa

Pressure and volume move oppositely

If temperature is constant, increasing pressure decreases volume and decreasing pressure increases volume.

When to use the combined gas law

If temperature changes, use a gas-law relationship that includes temperature rather than Boyle alone.

Constant-temperature assumption

Boyle's law assumes constant temperature and ideal-gas behaviour. Rapid compression, heating, cooling, and real gas behaviour can change the result.

Frequently asked questions

What stays constant in Boyle law?

Temperature and amount of gas stay constant.

Can I mix units?

Use matching pressure units and matching volume units on both sides.

What happens if pressure doubles?

Volume halves if temperature and gas amount stay constant.

Is this the same as ideal gas law?

It is a special case of gas behaviour when temperature and moles do not change.

Does this work for liquids?

No. It is intended for gases.

Related calculators

ideal-gas-law-calculator
pressure-calculator
volume-calculator

What does this mean?

This calculator is designed to help you understand the likely number before you make a decision or start an application.

Your result should be checked against official UK guidance, especially if your circumstances include dependants, exemptions, prior leave, or a complex immigration history.

Treat the figure as a planning tool rather than legal advice. Where the answer affects an application deadline or major payment, speak to an authorised adviser.