Ideal Gas Law Calculator
Calculate pressure, volume, temperature, or moles using the ideal gas law PV = nRT. Solve for any unknown variable.
Enter any three values to solve for the fourth. Leave one field empty.
Enter three values to solve for the fourth.
Ideal Gas Law
PV = nRT
R = 8.314 J/(mol·K)
R = 8.314 J/(mol·K)
Where P is pressure (Pa), V is volume (m³), n is amount of substance (moles), R is the gas constant, and T is absolute temperature (Kelvin).
Example: 1 mol of gas at 273.15 K and 101,325 Pa.
V = nRT / P = 1 × 8.314 × 273.15 / 101,325 = 0.02241 m³ (22.41 L)
V = nRT / P = 1 × 8.314 × 273.15 / 101,325 = 0.02241 m³ (22.41 L)
Key Values
| Constant/Condition | Value |
|---|---|
| R (gas constant) | 8.314 J/(mol·K) |
| Standard pressure | 101,325 Pa (1 atm) |
| Standard temperature | 273.15 K (0°C) |
| Molar volume at STP | 22.414 L/mol |
FAQ
When is the ideal gas law accurate?
It works well for real gases at low pressure and high temperature. At very high pressures or low temperatures, real gas behavior deviates (use van der Waals equation instead).
How do I convert °C to Kelvin?
K = °C + 273.15. Always use Kelvin in gas law calculations.
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Last updated: 2026-08-08