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Ideal Gas Law Calculator

Solve PV = nRT for pressure, volume, moles or temperature, plus combined, Boyle's and Charles's law modes with atm, kPa, bar, psi and mmHg units.

22.41397 L
Volume

V = nRT ÷ P

  • 22.41397 L
  • 0.022414 m³
  • Molar volume: 22.41397 L/mol
  • R = 8.314463 J/(mol·K) = 8.20574e-2 atm·L/(mol·K)
  • Temperatures are converted to kelvin before any division.

The ideal gas law assumes point-like molecules with no intermolecular forces. It is accurate for most gases near room temperature and around one atmosphere, but drifts at high pressure or close to the condensation point — real gases there need van der Waals or a compressibility factor.

What is the Ideal Gas Law Calculator?

The ideal gas law PV = nRT links pressure, volume, amount and temperature of a gas. With R = 8.3145 J/(mol·K), one mole at 0 °C and 1 atm occupies 22.41 litres.

  • Solves PV = nRT for P, V, n or T
  • Combined, Boyle's and Charles's law modes
  • Pressure in Pa, kPa, bar, atm, mmHg or psi
  • Volume in L, mL, m³ or ft³; temperature in K, °C or °F
  • Shows the gas constant in the units you chose
  • 100% browser-based, private and offline-capable

How to use the Ideal Gas Law Calculator

  1. 1

    Pick the gas law you need: ideal, combined, Boyle's or Charles's.

  2. 2

    Choose which variable to solve for.

  3. 3

    Select your pressure, volume and temperature units.

  4. 4

    Enter the known values and read the answer with its formula.

  5. 5

    Copy the result and the working if you need to show it.

About the Ideal Gas Law Calculator

The ByteTools Ideal Gas Law Calculator solves PV = nRT for whichever variable you are missing. Choose the unknown, enter the other three quantities in the units you actually measured them in, and the tool converts everything to SI internally, applies the gas constant and converts the answer back for you.

Alongside the full ideal gas law it offers the combined gas law P₁V₁/T₁ = P₂V₂/T₂ for before-and-after problems, plus dedicated Boyle's law and Charles's law modes. Temperatures entered in celsius or fahrenheit are converted to kelvin before any division, which is the single most common source of wrong answers in gas law homework.

Everything is calculated in your browser in JavaScript with no server involved. Results assume ideal behaviour, which is a good approximation near room temperature and ordinary pressures but drifts for real gases under extreme conditions.

Frequently asked questions

What is the ideal gas law formula?

PV = nRT, where P is pressure, V is volume, n is the amount of gas in moles, R is the universal gas constant and T is absolute temperature in kelvin. Rearranging it gives you any one variable from the other three.

What is the value of R in the ideal gas law?

R is 8.314 462 J/(mol·K) in SI units. In litre-atmospheres it is 0.082 057 L·atm/(mol·K), and in L·kPa it is 8.314. The calculator picks the right value automatically and displays it in the units you selected.

Why must temperature be in kelvin?

Because the gas laws involve dividing by temperature, and only an absolute scale gives the right proportionality. Using 25 instead of 298.15 makes the answer wrong by more than a factor of ten, so the tool converts celsius and fahrenheit for you.

What volume does one mole of gas occupy?

22.414 litres at 0 °C and 1 atm, the older definition of STP. Under IUPAC's current standard of 0 °C and 100 kPa the molar volume is 22.711 L, and at 25 °C and 1 atm it is about 24.47 L.

How accurate is the ideal gas law for real gases?

Very good near room temperature and around one atmosphere, typically within a percent or so. It becomes unreliable at high pressure or near the condensation point, where molecular volume and intermolecular attraction matter and a van der Waals equation or compressibility factor is needed.

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