Mole Fraction Calculator

Calculate the mole fraction and mole percent of each component in a mixture.

Mole fractions

Component	Moles	Mole fraction	Mole percent
Water	2.000 mol	0.6667	66.67%
Ethanol	1.000 mol	0.3333	33.33%

Total moles: 3.000 mol

Mole fractions sum to 1.0000

Mixture composition

Water 66.67% · Ethanol 33.33%

Try an example:

Total moles = 2 + 1 = 3.000 mol

Water mole fraction = 2.000 / 3.000 = 0.6667

Ethanol mole fraction = 1.000 / 3.000 = 0.3333

Water mole percent = 0.6667 × 100 = 66.67%

Ethanol mole percent = 0.3333 × 100 = 33.33%

Mole fraction tells you what fraction of all the moles in a mixture belongs to a particular component. It has no unit.

xᵢ = nᵢ / nₜₒₜₐₗ

where total moles are:

nₜₒₜₐₗ = n₁ + n₂ + ... + nₖ

Mole fraction uses moles, not mass. If you only know the mass of each substance, convert each mass to moles using its molar mass first.

Dividing mass directly instead of converting to moles

Forgetting to include every component in the total

Confusing mole fraction with molarity

Adding a unit to mole fraction — it has no unit

Forgetting that all mole fractions should add up to 1

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FAQ

What is the formula for mole fraction?

xᵢ = nᵢ / nₜₒₜₐₗ

Does mole fraction have a unit?

No. Mole fraction is dimensionless.

Do mole fractions always add up to 1?

Yes. The mole fractions of all components in the same mixture add up to 1, or 100% when expressed as percentages.

Can I calculate mole fraction from mass?

Yes. Convert each component's mass to moles using its molar mass, then divide each component's moles by the total moles.

What is the difference between mole fraction and mole percent?

Mole percent is simply mole fraction multiplied by 100.

Is mole fraction the same as molarity?

No. Mole fraction is based on the ratio of moles in a mixture, while molarity is moles per unit volume of solution.