Ideal Gas Molar Mass Calculator
Estimate a gas's molar mass from a measured sample mass and its absolute pressure, volume and temperature.
Calculate molar mass
Enter your gas sample measurements to calculate molar mass in g/mol.
Molar mass formula
Rearranging the ideal gas law and using sample mass allows molar mass to be estimated when the gas conditions are known.
M = mRT / PV
Assumptions and conditions
- The sample follows the ideal gas model.
- Mass is in grams, pressure in kPa, volume in litres and temperature in Kelvin.
- Pressure must be absolute pressure.
Frequently asked questions
What is molar mass?
Molar mass is the mass of one mole of a substance, usually expressed in g/mol.
How does the gas law find molar mass?
The ideal gas equation can be rearranged to M = mRT/(PV).
Which units should I enter?
Enter mass in grams, pressure in kPa, volume in litres and temperature in Kelvin.
Why must pressure be absolute?
The ideal gas equation requires absolute pressure rather than gauge pressure.
How to use this calculator
- Enter the measured sample mass in grams.
- Enter absolute pressure in kPa.
- Enter volume in litres.
- Enter temperature in Kelvin.
- Select Calculate molar mass to view the result.
Understanding the result
The calculated molar mass is reported in grams per mole (g/mol). The result assumes ideal-gas behaviour and depends on the accuracy of the mass, pressure, volume and temperature measurements.