Chemistry gas-law calculator

Boyle's Law Calculator

Calculate initial or final pressure and volume using P₁V₁ = P₂V₂ with automatic pressure and volume unit conversion.

Enter three known values

Solve Boyle's law

Free tool

The gas pressure before the change.

The gas volume before the change.

This is the value being calculated.

The gas volume after the change.

Boyle's law assumes a fixed amount of gas at constant temperature. Pressure and volume values are converted internally to SI units.

Try an example:

Result

Your result will appear here

Select the variable to calculate, enter the other three positive values, and choose the pressure and volume units.

Calculator guide

How this calculator works

Boyle's Law Calculator determines the relationship between pressure and volume of a gas when temperature remains constant. It helps chemistry students, researchers, and laboratory professionals calculate unknown pressure or volume values using Boyle's Law.

Formula explanation

Boyle's law describes the inverse relationship between gas pressure and volume when temperature remains constant.

Formula

Boyle's Law: P₁V₁ = P₂V₂

Worked example

Example: If pressure increases, gas volume decreases proportionally under constant temperature conditions.

Assumptions

  • Temperature remains constant during the calculation.
  • The gas behaves approximately as an ideal gas.
  • Pressure and volume units are compatible.

Examples

  • Example: Calculate the final gas volume when pressure changes while temperature remains constant.
  • Example: Scientists use Boyle's Law to study pressure-volume relationships in controlled gas experiments.

Common mistakes

  • Changing temperature during calculation.
  • Using inconsistent pressure units.
  • Confusing direct and inverse relationships.

Variables

  • Initial pressure
  • Initial volume
  • Final pressure
  • Final volume
  • Gas temperature assumption

Limitations

  • Accuracy decreases when gases behave differently from ideal gas assumptions.
  • The relationship applies only when temperature remains constant.

Scientific references

  • OpenStax Chemistry: Gas Laws
  • NIST Chemistry Reference Data
  • Scientific gas measurement guidelines

Content review

Reviewed by: ScienceCalcHub Chemistry Review Team | Last reviewed: 2026-08-30

Applications

  • Gas behavior analysis
  • Chemistry education
  • Laboratory gas calculations
  • Scientific experiments

Frequently asked questions

How is Boyle's Law calculated?

Boyle's Law is calculated by using the relationship between initial pressure, initial volume, final pressure, and final volume while temperature remains constant.

What does Boyle's Law describe?

Boyle's Law describes the inverse relationship between the pressure and volume of a gas at constant temperature.

What units can be used in Boyle's Law?

Any compatible pressure and volume units can be used as long as the same units are maintained on both sides of the equation.

Accuracy and transparency

Created and maintained by our editorial team

This chemistry calculator is maintained by the ScienceCalcHub Editorial Team. Its calculation logic is tested with representative inputs, while the supporting guidance is checked for formula clarity, units, assumptions, and common mistakes.

Written by
ScienceCalcHub Editorial Team
Reviewed by
ScienceCalcHub Scientific Review Team
Review standard
Formula accuracy, units, examples, and educational clarity

Learn more about our formula-review and correction process, explore our calculation methodology, or view our scientific references.

  • Calculation logic tested
  • Variables and units explained
  • Assumptions stated clearly
  • Corrections handled transparently

Chemistry overview

What is Boyle's law?

Boyle's law describes how the pressure and volume of a fixed amount of gas change when temperature remains constant. As volume decreases, pressure increases. As volume increases, pressure decreases.

This inverse relationship is commonly used to solve gas compression and expansion problems in chemistry and physics.

Formula

Boyle's law formula

Constant-temperature gas relationshipP₁V₁ = P₂V₂

  • P₁ is the initial gas pressure.
  • V₁ is the initial gas volume.
  • P₂ is the final gas pressure.
  • V₂ is the final gas volume.

Rearranged equations

Solve for pressure or volume

Initial pressure

P₁ = P₂V₂ ÷ V₁

Divide the final pressure-volume product by the initial volume.

Initial volume

V₁ = P₂V₂ ÷ P₁

Divide the final pressure-volume product by the initial pressure.

Final pressure

P₂ = P₁V₁ ÷ V₂

Divide the initial pressure-volume product by the final volume.

Final volume

V₂ = P₁V₁ ÷ P₂

Divide the initial pressure-volume product by the final pressure.

Worked example

Calculate pressure after compression

A gas has an initial pressure of 1 atm and an initial volume of 2 L. It is compressed to 1 L at constant temperature. Find the final pressure.

  1. Write the equation: P₁V₁ = P₂V₂.
  2. Rearrange it: P₂ = P₁V₁ ÷ V₂.
  3. Substitute the known values: P₂ = (1 atm × 2 L) ÷ 1 L.
  4. Calculate the result: P₂ = 2 atm.

Halving the volume doubles the pressure because pressure and volume are inversely proportional under Boyle's law.

Supported units

Pressure and volume units

The calculator converts values to consistent SI units before solving the equation, so supported units can be mixed safely.

  • Pressure: pascals, kilopascals, bar, atmospheres, and millimeters of mercury.
  • Volume: cubic meters, liters, and milliliters.
  • The calculated answer uses the unit selected for the unknown variable.

Required conditions

When Boyle's law applies

  • The temperature of the gas remains constant.
  • The amount of gas remains fixed.
  • No gas enters or leaves the system.
  • Pressure values are absolute rather than gauge pressure.
  • The gas behaves approximately as an ideal gas.

Inverse relationship

Understanding the pressure-volume graph

A graph of pressure against volume at constant temperature forms a downward curve called an isotherm. Equal increases in volume do not produce equal decreases in pressure because the relationship is inverse rather than linear.

A graph of pressure against reciprocal volume, 1/V, is linear when Boyle's law applies.

Calculation limits

Important limitations and mistakes

  • Do not use Boyle's law if the gas temperature changes significantly.
  • Do not substitute gauge pressure without first converting it to absolute pressure.
  • All entered pressure and volume values must be greater than zero.
  • Real gases can depart from ideal behavior at high pressure or near condensation.
  • Keep pressure and volume units physically consistent with their selected fields.

Related tools

Use the Ideal Gas Law Calculator when pressure, volume, moles, and temperature are involved.

Use the Pressure Calculator to calculate pressure from force and area.

Use the Density Calculator to calculate mass, volume, or density.

Questions and answers

Calculator FAQ

How is Boyle's Law calculated?

Boyle's Law is calculated by using the relationship between initial pressure, initial volume, final pressure, and final volume while temperature remains constant.

What does Boyle's Law describe?

Boyle's Law describes the inverse relationship between the pressure and volume of a gas at constant temperature.

What units can be used in Boyle's Law?

Any compatible pressure and volume units can be used as long as the same units are maintained on both sides of the equation.