Education
Ideal Gas Law Calculator
Last updated: June 19, 2026
The ideal gas law is an equation of state that describes the behavior of a hypothetical ideal gas, written as PV = nRT, where P is pressure, V is volume, n is the amount of substance in moles, R is the gas constant, and T is temperature. An ideal gas law calculator solves for any of these variables when the other four are provided. It supports conversions across multiple units of measurement. Physicists, chemical engineers, and students use it to analyze thermodynamic systems and gas behavior.
Pick what to solve for, choose units for pressure, volume, moles, and temperature, and the calculator returns the missing variable using PV = nRT. Inputs are normalized to L, atm, and K internally for a single value of R.
Quick Answer
Solve the ideal gas equation PV = nRT for pressure, volume, moles, or temperature. Input four variables to calculate the fifth.
Solve for
V unit
T unit
Ideal gas assumptions
- Particles have negligible volume.
- No intermolecular attractive forces.
- All collisions are perfectly elastic.
- Best at low pressures and high temperatures relative to the gas critical point.
Real gases deviate near condensation; for high-pressure or low-temperature work, use the van der Waals or another real-gas equation. Educational only.
Pressure
1.000619 atm
The calculator normalizes inputs to L, atm, mol, and K, applies PV = nRT with R = 0.082057 L·atm/(mol·K), then converts the output back to your chosen units.
Examples
1 mol at 0 °C, 1 atm
V = 22.4 L (molar volume)
2 mol at 25 °C, 5 L
P ≈ 9.78 atm
0.5 mol, 3 atm, 1.5 L
T ≈ 109.7 K
P = 2 atm, V = 10 L, T = 298 K
n ≈ 0.818 mol
How it works
The calculator converts your inputs to liters, atmospheres, moles, and kelvin, then applies the ideal gas relationship. Output values are converted back to your preferred display units.
Ideal gas law · PV = nRT
Gas constant · R = 0.082057 L·atm/(mol·K)
Other useful values: R = 8.314 J/(mol·K) and R = 62.364 L·mmHg/(mol·K).
Related chemistry and unit calculators
- Grams to moles calculator for converting gas mass to moles before plugging into PV = nRT.
- Pressure converter for switching between atm, kPa, Pa, mmHg, psi, and other pressure units.
- Volume converter for L, mL, m³, and other volume units.
- Temperature converter for K, °C, °F, and Rankine.
- All education calculators.
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Frequently asked questions
PV = nRT relates pressure (P), volume (V), moles (n), gas constant (R), and absolute temperature (T) for a hypothetical gas whose particles have no volume and no intermolecular forces. It is a useful approximation for most gases at normal lab conditions.
R = 0.082057 L·atm/(mol·K). Inputs in other units are converted to L, atm, mol, and K before the formula is applied, then the result is converted back to your chosen output unit.
Gas laws use absolute temperature. Celsius and Fahrenheit have arbitrary zero points and would give negative or unphysical results in the equation. The calculator accepts K, °C, or °F and converts internally.
Standard temperature and pressure has multiple definitions. IUPAC currently uses 0 °C (273.15 K) and 100 kPa. The older convention uses 0 °C and 1 atm. At the older STP, 1 mole of an ideal gas occupies 22.4 L (the molar volume).
Near condensation, at high pressure, or at very low temperature, gases deviate from ideal behavior. Use the van der Waals equation or a more accurate equation of state for those regimes.
No. The calculator is an educational tool. Do not use the output for laboratory preparation, gas-handling safety, or any other safety-critical decision; consult an instructor or a vetted procedure.
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