Mass Percent Calculator
Find percent by mass (w/w %) from the mass of solute and the mass of the whole solution — or solve for either mass when you know the percentage.
Quick answer: Mass percent = (mass of solute ÷ mass of solution) × 100. Dissolving 10 g of salt in 90 g of water makes 100 g of solution, so mass percent = (10 ÷ 100) × 100 = 10% w/w.
Mass of solution = mass of solute + mass of solvent.
Mass percent — also called percent by mass or w/w % — is the fraction of a solution's total mass that comes from the solute, times 100. It's the everyday concentration unit on product labels and in recipes, because it needs only a balance and doesn't depend on temperature or volume.
The formula
Mass percent = (mass of solute ÷ mass of solution) × 100
Solute = solution × percent ÷ 100 · Solution = solute × 100 ÷ percent
Solute = solution × percent ÷ 100 · Solution = solute × 100 ÷ percent
Worked example
A solution contains 25 g of sugar in 475 g of water. Total solution mass = 25 + 475 = 500 g. Mass percent = (25 ÷ 500) × 100 = 5% w/w.
Frequently asked questions
How do I calculate mass percent?
Divide the solute mass by the total solution mass and multiply by 100.
Does solution mass include the solute?
Yes. Solution mass = solute mass + solvent mass. Use the total, not just the solvent.
What's the difference from volume percent?
Mass percent uses masses (w/w); volume percent (v/v) uses volumes. They differ whenever densities differ.
What does w/w mean?
Weight for weight — the solute and solution are both measured by mass. It's the same as mass percent.
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