How this calculator works
Pressure multiplied by volume has units of energy. For a dilute equilibrium gas it equals the amount times R times kelvin temperature. This page fixes R to the exact SI value 8.31446261815324 J/(mol K). A mole counts entities; mass additionally needs the molar mass in kg/mol. Use a real-gas equation near saturation or at high density.
Formula
pV = nRT; n = pV/(RT); m = nM; M = m/n.
Worked example
One mole at 300 K in 0.02494338785 m³ has pressure 100000 Pa. Two moles with M = 0.028 kg/mol have mass 0.056 kg.
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Frequently asked questions
Is pressure absolute?
Yes. Add local atmospheric pressure to gauge pressure before using this equation.
Can temperature be zero?
No. This gas model requires a strictly positive kelvin temperature.
Can I enter grams per mole?
Divide by 1000 first: 28 g/mol is 0.028 kg/mol. The molar-mass field is explicitly in kg/mol.