Chemistry calculator
Mass Percent Calculator
Find percent by mass (w/w) and the implied solvent mass from a solution sample.
Mass percent
4% w/w
How the mass percent calculator works
Enter solute mass and the mass of the complete solution in the same unit. Because identical units cancel, grams are shown for convenience but another consistent mass unit gives the same percentage.
Total solution mass includes both solute and solvent. It must be positive and cannot be smaller than the solute mass; the remainder is displayed as solvent mass.
Worked example
A solution containing 10 g solute in 250 g total solution has 10÷250×100 = 4% w/w. Its solvent mass is 250−10 = 240 g. Using 0.010 kg and 0.250 kg gives the same 4%.
Assumptions and practical limits
This is mass percent, not volume percent or mass/volume percent. Density is required to move between mass and volume concentration.
The calculation assumes all entered solute belongs to the solution and does not correct for purity, hydration, evaporation, or measurement uncertainty.
Frequently asked questions
Is solution mass the solvent mass?
No. Solution mass is solute plus solvent.
Can I use kilograms?
Yes, if both masses use kilograms; matching units cancel.
Why can’t solute exceed solution mass?
The solute is part of the total solution, so that combination is physically inconsistent.