Mole fraction is the amount of one component divided by the total amount of every component in the mixture: xA = nA ÷ (nA + nB + …). For 1.00 mol ethanol in 10.0 mol water, xA = 1 ÷ 11 = 0.0909, so ethanol is 9.09 mol %. The fractions of all components always add up to 1.
Mole fraction is the concentration unit that colligative-property problems, Raoult's law and Dalton's law of partial pressures are written in, so general chemistry students and lab staff meet it constantly. Enter the amount in moles of component A and at least one other species; components C and D are optional for gas mixtures or ternary solutions. The result shows A's mole fraction as the headline, the mole percent, the fraction of every other component, the total amount, and a donut of how the moles split. The tool takes moles, not grams: convert masses first by dividing each by its molar mass, or the fractions will be weighted by mass instead of by particle count.
Type the amount in mol of the species whose mole fraction you need.
Fill in B, and C or D if the mixture has more species. Empty optional boxes are ignored.
The headline is xA; the stats list xB, xC, xD, the mole percent of A and the total moles, and the donut shows the split.
Result Mole fraction of A (xA): 0.3
Mole percent of A: 30%
Mole fraction of B: 0.7
Mole fraction of C: 0
Mole fraction of D: 0
Total amount: 10
A two-component mixture with 10 mol in total, so the solute's fraction is 3 out of 10.
Result Mole fraction of A (xA): 0.0909
Mole percent of A: 9.09%
Mole fraction of B: 0.9091
Mole fraction of C: 0
Mole fraction of D: 0
Total amount: 11
1.00 mol ethanol and 10.0 mol water; ethanol makes up about 9.09% of the molecules.
Result Mole fraction of A (xA): 0.2
Mole percent of A: 20%
Mole fraction of B: 0.5
Mole fraction of C: 0.3
Mole fraction of D: 0
Total amount: 10
With 10 mol of gas in total the fractions are 0.2, 0.5 and 0.3; by Dalton's law these are also the partial-pressure shares.
xi = ni ÷ (n1 + n2 + … + nk)
xinikIUPAC calls this the amount fraction. Each component's moles are divided by the sum of all moles, so the fractions are dimensionless, lie between 0 and 1 and sum to exactly 1. Multiplying by 100 gives mole percent. Because the value counts particles rather than mass, it does not change with temperature, unlike molarity, which depends on solution volume.
No. It is moles divided by moles, so the units cancel. It is reported as a plain number between 0 and 1, or as mole percent when multiplied by 100.
Divide each mass by that substance's molar mass to get moles, then enter those amounts. For example, 180 g of water at 18.015 g/mol is 9.99 mol, and 46 g of ethanol at 46.07 g/mol is 1.00 mol.
For an ideal gas mixture, Dalton's law gives the partial pressure of a gas as its mole fraction times the total pressure. A gas with x = 0.21 in air at 101.3 kPa has a partial pressure of about 21.3 kPa.
Each fraction is its component's share of the same total, so adding every share gives the total divided by itself. If your hand-worked fractions do not sum to 1, a component is missing or an arithmetic slip has crept in.
A mole fraction divides by the total of all components; a mole ratio divides one component by another. For 1 mol solute and 10 mol solvent the fraction is 0.0909, while the ratio is 0.1.
Raoult's law gives the vapour pressure of a solvent over an ideal solution as the solvent's mole fraction times the pure solvent's vapour pressure. Lowering the solvent fraction from 1 to 0.95 cuts its vapour pressure by 5%.
Using this tool in an assignment, article or report? Copy a citation, or a link for your website.
Tools Directory Editorial Team. (2026, October 23). Mole Fraction Calculator. Tools Directory. Retrieved October 27, 2026, from https://tools.milunir.com/chemistry/stoichiometry-and-reactions/mole-fraction-calculator/
Tools Directory Editorial Team. “Mole Fraction Calculator.” Tools Directory, 23 Oct. 2026, https://tools.milunir.com/chemistry/stoichiometry-and-reactions/mole-fraction-calculator/. Accessed 27 Oct. 2026.
Tools Directory Editorial Team. “Mole Fraction Calculator.” Tools Directory. Last modified October 23, 2026. Accessed October 27, 2026. https://tools.milunir.com/chemistry/stoichiometry-and-reactions/mole-fraction-calculator/.
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