Ideal Gas Law Calculator
Calculate the amount of gas in moles from its absolute pressure, volume, and temperature. Enter pressure in kPa, volume in litres, and temperature in Kelvin.
Ideal gas law
Calculate the amount of gas from pressure, volume, and temperature.
Enter positive values. Temperatures must be in Kelvin and pressures must be absolute, not gauge pressure.
Your answer will appear here
Enter your known values and select Calculate to see the result, formula, and solution steps.
Understanding the ideal gas law
The ideal gas law relates pressure, volume, temperature, and the amount of gas. When pressure, volume, and absolute temperature are known, the equation can be rearranged to calculate the number of moles.
PV = nRT
Assumptions and conditions
- The gas is approximated as an ideal gas.
- Pressure is absolute pressure in kPa.
- Volume is measured in litres and temperature in Kelvin.
- The gas constant used is 8.314462618 kPa·L/(mol·K).
Frequently asked questions
What is the ideal gas law?
The ideal gas law is PV = nRT, relating absolute pressure, volume, amount of gas, the gas constant, and absolute temperature.
What does this calculator find?
This calculator finds the amount of gas in moles from pressure, volume, and temperature.
Why must temperature be in Kelvin?
Gas-law equations use absolute temperature. Celsius values cannot be substituted directly into the ideal gas equation.
What units does this calculator use?
Enter pressure in kPa, volume in litres, and temperature in Kelvin. The gas constant is 8.314462618 kPa·L/(mol·K).
What is the ideal gas law formula?
The formula is PV = nRT. Rearranging it gives n = PV/(RT), which calculates the amount of gas in moles.
How to use this calculator
- Enter the absolute pressure in kPa.
- Enter the gas volume in litres.
- Enter the absolute temperature in Kelvin.
- Select Calculate result to find the amount of gas in moles.
Ideal gas law equation
The equation is PV = nRT. To calculate the amount of gas, rearrange it to n = PV/(RT). Here, P is absolute pressure, V is volume, n is the amount of gas in moles, R is the gas constant, and T is absolute temperature in Kelvin.
Check your units
This calculator uses kPa for pressure, litres for volume, and Kelvin for temperature. Convert other units before entering your values. The ideal gas law is an approximation, so results may differ from real-gas behaviour under high-pressure or near-condensation conditions.