Mass Percent Calculator
Find the mass percent (percent by weight) of a component from the solute and solvent masses.
How it works
mass % = (mass of component ÷ total mass of mixture) × 100 · total mass = component + rest
Mass percent (percent by weight, %w/w) is the mass of one component divided by the total mass of the whole mixture, times 100. It is temperature-independent because it uses only masses, which makes it a common way to state the strength of everything from alloys to laboratory reagents and food labels. The component and the rest of the mixture together make up the total.
Worked example
Dissolving 10 g of salt in 90 g of water gives a total of 100 g, so the salt is (10 ÷ 100) × 100 = 10% by mass.
Frequently asked questions
What is the difference between mass percent and volume percent?
Mass percent divides masses; volume percent divides volumes. They differ because components have different densities — 10% by mass is not generally 10% by volume.
Do I add the solute mass into the total?
Yes. The denominator is the whole mixture, so it includes both the component you are measuring and everything else. That is why the tool adds the two masses.
How does this relate to concentration?
Mass percent is one way to express concentration by weight. For solutions labelled by molarity you would instead need moles per litre, which the molarity calculators provide.
Related calculators
Educational estimate. Check the formula, units and significant figures for your exact case.