When does the ideal gas law apply?

It works well at low pressures and high temperatures where gas molecules are far apart. It becomes inaccurate near condensation or at very high pressures.

What value of R should I use?

R = 0.08206 L·atm/(mol·K) for pressure in atm and volume in liters. R = 8.314 J/(mol·K) for SI units.

How do I convert Celsius to Kelvin?

Add 273.15. For example, 25°C = 298.15 K. Temperature in the ideal gas law must be in Kelvin.

Free Ideal Gas Law Calculator

Calculate pressure, volume, moles, or temperature of an ideal gas using PV = nRT.

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Amount of Gas (n)

mol

Temperature (T)

Volume (V)

Pressure (P)

1.0000 atm

Pressure101.33 kPa

Pressure (P) vs Amount of Gas (n)

View formula & how it works →

Ideal Gas Law

Formula

PV = nRT

Solving for P: P = nRT / V

Where:

P = pressure (atm)

V = volume (L)

n = moles of gas

R = gas constant = 0.08206 L·atm/(mol·K)

T = temperature (K)

The ideal gas law assumes no intermolecular forces and negligible molecular volume.

Example Calculation

1 mole of gas at 273.15 K (0°C) in 22.414 L.

01P = nRT / V
02P = (1)(0.08206)(273.15) / 22.414
03P = 22.414 / 22.414
04P = 1.000 atm

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