What is the Ideal Gas Law Calculator?
The ideal gas law PV = nRT relates pressure, volume, amount of gas (moles), and temperature for an ideal gas. Enter any three variables and solve for the fourth — pressure, volume, moles, or temperature. Supports atm, kPa, mmHg, and Pa for pressure; liters and milliliters for volume; kelvin and Celsius for temperature. Optionally enter molar mass to estimate gas density. Uses R = 0.082057 L·atm/(mol·K). Runs instantly in your browser with no signup.
How to use the Ideal Gas Law Calculator
- Choose which variable to solve: P, V, n, or T.
- Enter the three known values with appropriate units.
- Optionally add molar mass (g/mol) to calculate density.
- Read the solved value and full PV = nRT breakdown.
- Copy the summary for homework or lab notes.
Common use cases
- Finding volume of 1 mol at STP (≈22.4 L at 1 atm, 273 K)
- Calculating pressure of 0.5 mol in 10 L at room temperature
- Solving for moles from lab P, V, and T measurements
Frequently asked questions
- What is the ideal gas law?
- PV = nRT, where P is pressure, V is volume, n is moles, T is temperature in kelvin, and R is the gas constant (0.082057 L·atm/(mol·K)).
- What is molar volume at STP?
- At standard temperature and pressure (0 °C, 1 atm), one mole of an ideal gas occupies about 22.4 L.
- Can I use Celsius?
- Yes — the calculator converts °C to kelvin automatically (K = °C + 273.15) before applying the equation.
- When does the ideal gas law fail?
- Real gases deviate at very high pressures or very low temperatures where intermolecular forces and molecular volume matter.
