Ideal Gas Law Calculator

PV = nRT, solving for whichever term is missing.

Written and maintained by Mohit PatelLast checked August 4, 2026How we build these

Solve for

Pressure

Moles

mol

Temperature

°C

Real gases depart from this at high pressure and near their condensation point, where molecular volume and intermolecular attraction stop being negligible. For everyday conditions the error is under a percent; near liquefaction it is large.

Volume (m³)

0.02241

22.414 litres · 273.15 K

Pressure101,325 Pa

Volume0.022414 m³

In litres22.414

Moles1

Temperature0 °C

In kelvin273.15

Molar volume at STP22.414 L/mol

PV = nRT, with R exactly 8.31446261815324 J/(mol·K) — a defined constant since the 2019 SI redefinition rather than a measured one. Temperature must be absolute: the equation uses kelvin, and using Celsius directly is the single commonest error here. One mole at 0 °C and one atmosphere occupies 22.41 litres regardless of which gas it is.

How the Ideal Gas Law Calculator works

PV = nRT, with R exactly 8.31446261815324 J/(mol·K) — a defined constant since the 2019 SI redefinition rather than a measured one. Temperature must be absolute, and using Celsius directly is the commonest error here.

Also known as: pv = nrt calculator · gas law calculator · molar volume calculator · ideal gas equation

Where to go next

The Ideal Gas Law question rarely arrives on its own. These are the ones that usually come with it:

Molarity Calculator — Moles per litre of solution — not of solvent.
Pressure Calculator — From a force on an area, or from a depth of fluid.
Boiling Point Calculator — Water's boiling point at altitude, from the pressure.
Molar Volume Calculator — STP is ambiguous — 22.414 and 22.711 are both correct.

Sources

Frequently asked questions

What is the ideal gas law?

PV = nRT — pressure times volume equals moles times the gas constant times absolute temperature. It relates all four quantities, so any three give the fourth.

What volume does one mole of gas occupy?

22.41 litres at 0 °C and one atmosphere, regardless of which gas it is. That result — equal volumes of any gas hold equal numbers of molecules — is Avogadro's law.

Why must I use kelvin?

Because the equation is proportional to absolute temperature. Using Celsius makes 0° into zero, which would imply a gas has no volume at freezing point. Add 273.15.

When does the ideal gas law break down?

At high pressure and near condensation, where molecular volume and intermolecular attraction stop being negligible. For everyday conditions the error is under a percent.

Put this calculator on your own site

Free to use, on any site, commercial or not. Paste this where you want it to appear. It is a plain iframe, so it works in WordPress, Squarespace, Wix, Webflow, Ghost and anything else that accepts HTML.

The one-line version

<iframe src="https://www.thecalclibrary.com/embed/ideal-gas-law-calculator" width="100%" height="640" style="border:1px solid #e2e8f0;border-radius:12px" loading="lazy" title="Ideal Gas Law Calculator"></iframe>
<p style="font:13px/1.5 system-ui,sans-serif;margin:6px 0 0;color:#64748b">Powered by <a href="https://www.thecalclibrary.com/ideal-gas-law-calculator" style="color:#64748b">Ideal Gas Law Calculator</a> from The Calc Library</p>

The only condition is that the credit line below the frame stays in place. That one line is what pays for the tool being free — it is how anyone else finds it.