Mass Percent Calculator
Find the mass percent of a solution — the mass of solute as a percentage of the total. Enter the solute mass and either the solvent mass or the total solution mass (in the same units) to get percent by mass and the equivalent in ppm.
Example: with Solute mass (g) 20 · Second mass (g) 130 · The second mass is the… solvent (added to solute) → Mass percent: 13.333% by mass.
- Solution mass150 g solution
- As ppm133,333 ppm
Computed by the calculator below using its default values. Change any input to see your own numbers.
Mass percent = (mass of solute ÷ mass of solution) × 100. The mass of solution is the solute plus the solvent, so both go into the denominator.
Mass of solute over mass of solution
Mass percent tells you how much of a mixture's weight is one component. Divide the solute mass by the total solution mass and multiply by 100. The key is the denominator: it is the whole solution — solute plus solvent — not just the solvent. Dissolving 20 g of salt in 130 g of water makes 150 g of solution, so the salt is 20/150 = 13.3% by mass.
Because it is a ratio of masses, mass percent is independent of temperature and needs no molar masses, which makes it the common way to label commercial solutions: 3% hydrogen peroxide, 5% acetic acid in vinegar, 0.9% saline. Multiply a mass percent by 10,000 to read it as parts per million, useful once concentrations drop well below 1%.
How it’s calculated
Mass percent = (m_solute / m_solution) × 100, where m_solution is either the solute plus solvent (solvent mode) or the total mass you enter (solution mode). Parts per million is mass percent × 10,000. The solute and second mass must share the same units.
Masses are additive with no volume change on mixing. The result is a weight/weight percent (w/w), not weight/volume.
Mass percent of everyday solutions
| Solution | Mass percent (w/w) |
|---|---|
| Normal saline | 0.9% |
| Seawater (total dissolved salts) | ≈ 3.5% |
| Household vinegar (acetic acid) | ≈ 5% |
| Hydrogen peroxide (drugstore) | 3% |
| Household bleach (sodium hypochlorite) | 5–8% |
Typical label and reference values; rounded.
Common mistakes
- Dividing by the solvent mass alone instead of the total solution mass.
- Mixing units — the solute and solution masses must be in the same unit before dividing.
- Confusing weight/weight percent with weight/volume percent (g per 100 mL).
- Reading a percent above 100%, which means the solute mass exceeds the solution mass — an input error.
Frequently asked questions
What is the mass percent formula?
Mass percent = (mass of solute ÷ mass of solution) × 100. The mass of solution includes both the solute and the solvent.
Does the solvent or the solution go in the denominator?
The total solution. That is the solute plus the solvent. Using only the solvent overstates the percentage.
How do I convert mass percent to ppm?
Multiply by 10,000. A 0.01% solution is 100 ppm, because percent is parts per hundred and ppm is parts per million.
Is mass percent affected by temperature?
No. It is a ratio of masses, and mass does not change with temperature, so mass percent stays constant even as volume expands or contracts.