How this calculator works
Mass percentage uses the complete solution mass in the denominator. If you know solvent mass instead, add solute and solvent first. No density is required and there is no assumption about volume additivity. The separate grams-per-100-g-solvent output uses a different denominator and is omitted for a pure solute. No material can contribute more mass than the full mixture.
Formula
Mass fraction w = msolute/msolution. Mass percent = 100 w. Solution mass = solute mass + solvent mass.
Worked example
Ten grams solute in 100 g total solution is 10% by mass and contains 90 g solvent. A 200 g solution at 25% requires 50 g solute and 150 g solvent.
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Frequently asked questions
Is 10 g in 100 g water a 10% solution?
No. The total mass is 110 g, so the mass percentage is about 9.09%.
Can mass percentage equal 100%?
Yes. That is the pure component limit, with no solvent.
Is mass percent affected by temperature?
The mass ratio is unchanged by thermal expansion, although evaporation or reaction can change composition.