Chemistry gas-law calculator

Ideal Gas Law Calculator

Calculate pressure, volume, moles, or temperature using PV = nRT with automatic unit conversion.

Enter three known values

Solve the ideal gas law

Free tool

This is the value being calculated.

The volume occupied by the gas.

mol

The amount of gas in moles.

The absolute temperature of the gas.

All values are converted internally to SI units. Temperature must remain above absolute zero.

Try an example:

Result

Your result will appear here

Select the variable to calculate, enter the other three values, and choose their units.

Calculator guide

How this calculator works

Ideal Gas Law Calculator determines the relationship between pressure, volume, temperature, and amount of gas using the ideal gas equation. It helps students, researchers, scientists, engineers, and laboratory professionals analyze gas behavior, thermodynamic relationships, and experimental measurements accurately.

Formula explanation

The ideal gas law relates pressure, volume, temperature, and amount of gas using the equation PV = nRT.

Formula

PV = nRT

Worked example

Example: Gas pressure can be calculated when volume, temperature, and number of moles are known.

Assumptions

  • The gas behaves approximately as an ideal gas.
  • Temperature values are converted to compatible units.
  • Pressure, volume, and mole measurements are accurate.
  • Pressure and temperature conditions allow reasonable ideal gas approximation.
  • Real gas effects may require advanced correction models under extreme conditions.

Examples

  • Example: Gas pressure can be calculated when volume, temperature, and number of moles are known.
  • Example: Scientists use the ideal gas law to estimate gas properties in laboratory experiments.

Common mistakes

  • Using incorrect temperature units.
  • Forgetting pressure unit conversions.
  • Using the wrong gas constant.

Variables

  • Pressure
  • Volume
  • Temperature
  • Number of moles
  • Ideal gas constant
  • Universal gas constant (R)
  • Molar volume
  • Gas density
  • Calculated gas property

Limitations

  • Real gases may differ from ideal behavior at high pressure or low temperature.
  • Accuracy depends on correct measurements and unit conversions.

Scientific references

  • OpenStax Chemistry: The Ideal Gas Law
  • 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
  • Laboratory gas calculations
  • Chemistry education
  • Scientific research
  • Thermodynamics studies
  • Engineering calculations
  • Chemical process analysis
  • Industrial gas systems

Frequently asked questions

What is the ideal gas law?

The ideal gas law describes the relationship between pressure, volume, temperature, and number of moles using the equation PV = nRT.

What variables are used in the ideal gas law?

The ideal gas law uses pressure, volume, temperature, amount of gas, and the ideal gas constant.

When does the ideal gas law work best?

The ideal gas law works best when gas particles have minimal interactions and the gas behaves close to an ideal model.

How is an unknown value calculated using PV = nRT?

An unknown gas property is calculated by rearranging the ideal gas equation while keeping the other known variables constant.

Where is the ideal gas law used?

The ideal gas law is used in chemistry laboratories, engineering calculations, thermodynamics studies, industrial gas systems, and scientific research.

What is the ideal gas constant?

The ideal gas constant R is a proportionality constant used in the ideal gas equation to relate pressure, volume, temperature, and amount of gas.

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 the ideal gas law?

The ideal gas law describes the relationship between the pressure, volume, amount, and absolute temperature of an ideal gas. It combines several simpler gas laws into one equation: PV = nRT.

The equation is widely used in chemistry and physics to estimate the behavior of gases when three of the four main variables are known.

Formula

Ideal gas law formula

Ideal gas lawPV = nRT

  • P is the pressure of the gas.
  • V is the volume occupied by the gas.
  • n is the amount of gas in moles.
  • R is the universal gas constant.
  • T is absolute temperature in kelvin.

Rearranged equations

Solve for any gas variable

Pressure

P = nRT ÷ V

Divide nRT by the gas volume.

Volume

V = nRT ÷ P

Divide nRT by the gas pressure.

Moles

n = PV ÷ RT

Divide pressure times volume by RT.

Temperature

T = PV ÷ nR

Divide pressure times volume by nR.

Worked example

Find the volume of one mole at 25°C

Suppose one mole of an ideal gas is at 1 atmosphere and 25°C. Calculate its volume using V = nRT ÷ P.

  1. Convert the temperature: 25°C = 298.15 K.
  2. Convert pressure to SI units: 1 atm = 101,325 Pa.
  3. Substitute the values into V = nRT ÷ P.
  4. Calculate the volume: V ≈ 0.02447 m³.
  5. Convert cubic meters to liters: V ≈ 24.47 L.

Supported units

Pressure, volume, and temperature units

This calculator automatically converts common laboratory units to SI units before applying the equation.

  • Pressure: pascals, kilopascals, bar, atmospheres, and millimeters of mercury.
  • Volume: cubic meters, liters, and milliliters.
  • Temperature: kelvin, degrees Celsius, and degrees Fahrenheit.
  • Amount of gas: moles.

Gas constant

Why the value of R depends on units

The universal gas constant can be written in different numerical forms depending on the selected pressure and volume units. For example, it is often shown as approximately 8.314 J/(mol·K) in SI calculations or 0.082057 L·atm/(mol·K) in laboratory problems.

This tool avoids mixing incompatible versions of R by converting all values internally and using the SI gas constant.

Model assumptions

When the ideal gas law works best

  • Gas particles are treated as having negligible individual volume.
  • Intermolecular attractions and repulsions are assumed to be negligible.
  • Particle collisions are treated as perfectly elastic.
  • The model usually works best at relatively low pressure and high temperature.

Calculation limits

Important limitations

Real gases can depart from ideal behavior at high pressures, low temperatures, or near a phase change. More advanced equations, such as the van der Waals equation, may be required under those conditions.

  • Pressure, volume, and moles must be greater than zero.
  • Temperature must be above absolute zero.
  • Units must describe the physical quantities shown.
  • Results are estimates based on ideal gas behavior.

Related tools

Use the Pressure Calculator for force-per-area calculations.

Use the Molarity Calculator to calculate concentration from moles and solution volume.

Use the Stoichiometry Calculator for mole-ratio calculations in balanced chemical reactions.

Questions and answers

Calculator FAQ

What is the ideal gas law?

The ideal gas law describes the relationship between pressure, volume, temperature, and number of moles using the equation PV = nRT.

What variables are used in the ideal gas law?

The ideal gas law uses pressure, volume, temperature, amount of gas, and the ideal gas constant.

When does the ideal gas law work best?

The ideal gas law works best when gas particles have minimal interactions and the gas behaves close to an ideal model.

How is an unknown value calculated using PV = nRT?

An unknown gas property is calculated by rearranging the ideal gas equation while keeping the other known variables constant.

Where is the ideal gas law used?

The ideal gas law is used in chemistry laboratories, engineering calculations, thermodynamics studies, industrial gas systems, and scientific research.

What is the ideal gas constant?

The ideal gas constant R is a proportionality constant used in the ideal gas equation to relate pressure, volume, temperature, and amount of gas.