Ideal Gas Law Calculator
Choose the unknown in PV = nRT and enter the other three quantities. The calculator converts pressure, volume and temperature to SI, solves the equation, and returns the answer in your selected units.
Enter your values or load an example. Calculations stay in this browser.
Start with absolute pressure
An ideal-gas calculation uses absolute pressure. If your instrument gives gauge pressure, first convert it using the appropriate ambient pressure. Enter volume for the whole gas sample and amount in moles.
Temperature must be above absolute zero
The calculation uses Kelvin internally. Celsius and Fahrenheit are converted before substitution; values at or below absolute zero are rejected. A negative Celsius temperature can still be a valid gas temperature.
Check the familiar one-mole example
At 273.15 K and 101.325 kPa, one mole occupies about 22.414 L in the ideal model. Load the example, choose volume, and compare the displayed SI inputs with the final litre conversion.
Know when the model is an approximation
The ideal law relates pressure, volume, temperature and amount without accounting for molecular volume or attractions. Real gases can depart from it at high pressure or near condensation. Use an appropriate real-gas model when the application requires it.
Related free tools
Sources and methods
Frequently Asked Questions
Can I solve for temperature?
Yes. Select temperature and enter positive pressure, volume and moles. The answer can be shown in K, °C or °F.
Is gauge pressure accepted?
No. Enter absolute pressure. The calculator does not assume an ambient pressure for a gauge conversion.
Which gas constant is used?
R = 8.31446261815324 J/(mol·K). Inputs are converted to pascals, cubic metres and Kelvin before calculation.
Can I enter zero pressure or volume?
No. This model requires positive absolute pressure, volume and amount, and a temperature above absolute zero.
Continue in the app
Use Chemistry AI: Chymia for the full guided result after this quick check.
