Ideal Gas Law Calculator Formula
Understand the math behind the ideal gas law calculator. Each variable explained with a worked example.
Formulas Used
Pressure (P)
pressure = (n * 0.08206 * temp) / volumePressure
pressure_kpa = ((n * 0.08206 * temp) / volume) * 101.325Variables
| Variable | Description | Default |
|---|---|---|
n | Amount of Gas (n)(mol) | 1 |
temp | Temperature (T)(K) | 273.15 |
volume | Volume (V)(L) | 22.414 |
How It Works
Ideal Gas Law
Formula
PV = nRT
Solving for P: P = nRT / V
Where:
The ideal gas law assumes no intermolecular forces and negligible molecular volume.
Worked Example
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
Frequently Asked Questions
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.
Learn More
Guide
How to Use the Ideal Gas Law
Learn how to use the ideal gas law PV = nRT step by step. Covers pressure, volume, temperature, moles, the gas constant, and related gas laws with worked examples.
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Open Ideal Gas Law Calculator