％ Mass Percent (w/w) Calculator
Enter the mass of solute and solvent to get the mass percent (%w/w) — the concentration on reagent and nutrition labels.
Mass percent (w/w)
10%
Total solution mass
100 g
Mass percent by weight (%w/w) = mass of solute ÷ total mass of solution × 100, where the solution mass is solute + solvent. It's the concentration on nutrition and reagent labels — a 10 g solute in 90 g water is a 10% (w/w) solution. 🔒 In your browser.
How the mass percent (w/w) calculator works
Mass percent by weight is %(w/w) = mass of solute ÷ mass of solution × 100, where the solution's mass is the solute plus the solvent. The tool adds your two masses to get the solution mass and computes the percentage. Any consistent mass unit works — grams in, grams out — since the units cancel in the ratio.
Mass percent is distinct from percent composition (the mass fraction of each element within a compound's formula) and from ppm (used for trace amounts). It's the everyday "how concentrated is this solution" figure — a 0.9% saline drip, a 3% hydrogen-peroxide bottle, a 70% isopropyl alcohol.
Frequently asked questions
How do you calculate mass percent?
Mass percent (w/w) = mass of solute ÷ total mass of solution × 100. Dissolve 10 g of salt in 90 g of water and the solution is 10 g ÷ 100 g × 100 = 10% salt by mass.
What is the difference between %w/w and %w/v?
Mass percent (w/w) is grams of solute per 100 g of solution; weight/volume percent (w/v) is grams per 100 mL of solution. This tool computes w/w; for w/v you'd divide by the solution's volume instead of its mass.
Is mass percent the same as percent composition?
No. Percent composition is the mass fraction of each element inside a compound (from its formula). Mass percent here is the fraction of solute in a solution. Use the percent-composition tool for the former.
How do I make a 10% solution?
Make the solute 10% of the total mass: for 100 g of a 10% solution, use 10 g of solute and 90 g of solvent. Scale as needed — 25 g solute + 225 g solvent is also 10%.
What mass unit should I use?
Any, as long as both masses use the same one, because the units cancel in the ratio. Grams are usual in the lab; the percentage comes out the same whether you use grams or kilograms.