Air - Composition and Molecular Weight

Calculate the average molar mass of air based on the composition of its major components (Nitrogen, Oxygen, Argon, and other trace gases). The tool uses the mole fraction and molar mass of each gas component to determine the overall molecular weight of dry air.

Air Composition and Molecular Weight Calculator

Air is a mixture of gases. The average molar mass is calculated using:

M_mixture = x₁M₁ + x₂M₂ + ... + xₙMₙ

Where:

xᵢ = mole fractions of each gas
Mᵢ = molar mass of each gas

The molar mass of dry air is approximately 28.9647 g/mol.

Calculator

Inputs

Nitrogen (N₂) Mole Fraction (mol/mol)

Nitrogen Molar Mass (g/mol)

Oxygen (O₂) Mole Fraction (mol/mol)

Oxygen Molar Mass (g/mol)

Argon (Ar) Mole Fraction (mol/mol)

Argon Molar Mass (g/mol)

Carbon Dioxide (CO₂) Mole Fraction (mol/mol)

Carbon Dioxide Molar Mass (g/mol)

Results

Nitrogen Contribution-- g/mol

Oxygen Contribution-- g/mol

Argon Contribution-- g/mol

Carbon Dioxide Contribution-- g/mol

Average Molar Mass of Air-- g/mol

Component	Formula	Mole Fraction	Molar Mass (g/mol)	Volume %
Nitrogen	N₂	0.78084	28.013	78.084
Oxygen	O₂	0.20946	31.999	20.946
Argon	Ar	0.00934	39.948	0.934
Carbon Dioxide	CO₂	0.000412	44.010	0.0412
Neon	Ne	0.00001818	20.180	0.001818
Helium	He	0.00000524	4.003	0.000524
Methane	CH₄	0.00000179	16.042	0.000179
Krypton	Kr	0.0000010	83.798	0.0001
Hydrogen	H₂	0.0000005	2.016	0.00005
Xenon	Xe	0.00000009	131.293	0.000009