ChemBench

Ideal Gas Law Calculator

PV = nRT, solved for pressure.

Volume (L)

Moles (n)

Temperature (K)

Pressure

1.001 atm

PV = nRT, solved for P

What you entered

Volume (L): 22.4Moles (n): 1Temperature (K): 273.15

1
P = nRT ÷ V
(1 × 0.0821 × 273.15) ÷ 22.4= 1.0011 atm

Result

Pressure: 1.001 atm

At these conditions, the gas exerts 1.001 atm of pressure.

Pressure from the ideal gas law

PV = nRT, solved for pressure. These rows use R = 0.0821 L atm per mol per kelvin, the value most courses use.

Volume	Moles	Temperature	Pressure
22.414 L	1	273.15 K (0 C)	1.0005 atm
24.45 L	1	298.15 K (25 C)	1.0011 atm
22.414 L	1	298.15 K (25 C)	1.0921 atm
10 L	0.5	300 K	1.2315 atm
5 L	2	350 K	11.4940 atm
1 L	1	273.15 K	22.4256 atm

One mole of any ideal gas occupies 22.414 L at 0 C and 1 atm, and 24.45 L at 25 C. The first two rows come out fractionally above 1 atm only because R is rounded to 0.0821.

One equation, four connected variables

The ideal gas law links pressure, volume, moles, and temperature into a single relationship — change any one (holding the others' relationships fixed) and the rest respond predictably.

Why 'ideal' — and when that's a fine approximation

Real gases deviate from this law at very high pressure or very low temperature, but at typical everyday conditions the ideal gas law is accurate enough for nearly all chemistry and engineering calculations.

Frequently asked questions

I have 2 mol of gas at 300 K in a 10 L container — what is the pressure?

P = nRT/V = 2 × 0.08206 × 300 / 10 = 4.92 atm.

How is the ideal gas law different from Boyle's or Charles's law?

Boyle's law (P vs V at constant T) and Charles's law (V vs T at constant P) are each special cases of PV = nRT. The ideal gas law combines all variables into one equation, while the individual laws hold one variable fixed. Use the Boyle's law or Charles's law calculators when only one variable changes.

When does the ideal gas law break down?

At high pressures (above ~10 atm) or low temperatures (near a gas's boiling point), real molecules interact and occupy volume. The van der Waals equation corrects for this but is rarely needed for everyday lab conditions.

Which value of R should I use?

Use R = 0.08206 L·atm/(mol·K) if pressure is in atm and volume in liters. Use R = 8.314 J/(mol·K) for SI units (Pa and m³). Mixing units is the most common source of errors.