Ideal Gas Law Calculator
Solve PV = nRT with pressure, volume, mole, and temperature units.
Solve PV = nRT for any one variable. Mixed units are fine: everything is converted to atm, litres, moles, and kelvin before the equation is applied, then converted back for the answer.
R = 0.0820574 L·atm/(mol·K) = 8.31446 J/(mol·K). The ideal gas law assumes no intermolecular forces and negligible particle volume.
How to Use the Ideal Gas Law Calculator
1
Choose the unknown. Select whether you are solving for pressure, volume, moles, or temperature.
2
Enter values with any units. Type the three known quantities and pick their units — atm, kPa, mmHg, bar, psi, litres, millilitres, Celsius, Fahrenheit, or kelvin all work.
3
Read the converted answer. The result shows the solved value in your chosen unit, every input converted to atm, litres, moles, and kelvin, plus molar volume and particle count.
What is the Ideal Gas Law Calculator?
The ideal gas law calculator solves PV = nRT for any variable — pressure, volume, moles, or temperature — with unit handling for atm, kPa, mmHg, liters, milliliters, Celsius, and Kelvin. The gas constant R is applied in units that match your inputs.
Most gas law mistakes are unit mistakes: forgetting to convert Celsius to Kelvin, or mixing kPa with atm. The calculator normalizes units before solving and shows the converted values, which is exactly the habit to copy in hand calculations.
Common Uses
- Solve for pressure, volume, moles, or temperature
- Convert between gas law unit systems
- Find molar volume at STP or lab conditions
- Check gas stoichiometry homework
How to Solve It by Hand
Manual calculation is still important: identify the known variables, convert units before substitution, apply the equation, and check whether the result is chemically reasonable. The most common mistakes are inconsistent units, constants rounded too early, and skipping the interpretation step.
Practice Prompt
Try changing the default values and ask the lower-right chemistry chat why the result increased or decreased. That turns the calculator from a number machine into a study loop.
PV = nRT relates pressure, volume, moles of gas, and absolute temperature through the gas constant R. With pressure in atm, volume in litres, and temperature in kelvin, R = 0.0820574 L·atm/(mol·K).
The relationship is proportional to absolute temperature. Using Celsius makes 0 degrees look like zero thermal energy, which produces nonsense such as infinite pressure or zero volume. Always add 273.15 first — the calculator does this automatically.
Match R to your units. Use 0.0820574 L·atm/(mol·K) with atm and litres, or 8.31446 J/(mol·K) with pascals and cubic metres. This calculator normalises every input to atm, litres, moles, and kelvin, so you can mix kPa with mL safely.
At 0 °C and 1 atm, one mole of an ideal gas occupies 22.414 L. At SATP (25 °C and 1 bar) it is 24.79 L. Both presets are built into the calculator.
At high pressure (roughly above 10 atm) and at temperatures near condensation, where intermolecular forces and finite molecular volume matter. The van der Waals equation corrects for both.