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Ideal gas law calculator

Solve the ideal gas equation (PV = nRT) and the combined gas law (P1V1/T1 = P2V2/T2): enter the known values in atm, kPa, mmHg, liters and °C and find what's missing.

How to use

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Ideal gas equation

Leave blank only the value you want to calculate.

Available in: PortuguêsEspañolEnglish

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Ideal gas law calculator: what it is for

Choose between the ideal gas equation and the combined gas law, select the units for pressure (atm, kPa, mmHg, bar, Pa), volume (L, mL, m³) and temperature (°C or K) and leave blank the value you want to find. The tool converts temperature to kelvin, uses R = 0.082057 atm·L/(mol·K) and identifies whether the process is isothermal, isobaric or isochoric.

Calculations run in your browser.

How to use

  1. Choose the equation and units.
  2. Fill in the known values.
  3. See the calculated value.

When to use it

  • Solving chemistry gas problems.
  • Calculating gas volume in reactions.
  • Studying Boyle's, Charles's and Gay-Lussac's laws.

Frequently asked questions

What is the ideal gas law?

It's the equation PV = nRT. P is pressure, V volume, n the amount in moles, T the temperature in kelvin and R the universal gas constant, 0.082057 atm·L/(mol·K) or 8.314 J/(mol·K).

Why does the temperature have to be in kelvin?

Gas laws are proportional to absolute temperature. In °C, zero isn't the point of minimum energy and the calculations would be wrong. The tool converts automatically: K = °C + 273.15.

When do I use the combined gas law?

When the same amount of gas goes from one state to another. Isothermal (Boyle), isobaric (Charles) and isochoric (Gay-Lussac) processes are special cases where one quantity stays constant.

Is it really free?

Yes, 100% free. No sign-up, no subscription and no usage limits. All Tools123 tools are free and run right in your browser.

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