Ideal Gas Law Calculator
Solve PV = nRT for pressure, volume, moles, or temperature with metric and imperial support.
How it works
- 1Select which variable to solve for — pressure, volume, amount (moles), or temperature.
- 2Enter the three known values. Temperature accepts °C (metric) or °F (imperial) and is converted to kelvin internally.
- 3The result uses PV = nRT with R = 8.314 J/(mol·K), shown with equivalent values in common units.
Use cases
- Chemistry students checking gas-phase reaction conditions and stoichiometry.
- Engineers estimating compressed-gas tank volumes or storage pressures.
- Lab technicians confirming a gas sample behaves ideally at standard conditions.
Frequently asked questions
What is the ideal gas law formula?
PV = nRT, where P is pressure in pascals, V is volume in cubic metres, n is the amount of gas in moles, R is the universal gas constant 8.314 J/(mol·K), and T is the absolute temperature in kelvin.
Why must temperature be in kelvin, not Celsius?
The law needs an absolute scale. At 0 °C (273.15 K) a gas still has a positive volume; using Celsius would give nonsense at or below 0 °C. Always convert °C to K by adding 273.15.
Can you show a worked example?
At STP — 1 mol at 0 °C (273.15 K) and 101.325 kPa: V = nRT ÷ P = (1 × 8.314 × 273.15) ÷ 101,325 ≈ 0.02241 m³ = 22.41 L, the standard molar volume of an ideal gas.
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