Mass Percent Calculator

How to use this calculator

Enter the mass of the dissolved substance (solute) and of the liquid it is dissolved in (solvent) to get the mass percent. To make up a solution, enter the percentage you want and the total mass of solution — the calculator splits it into solute and solvent masses for you.

Mass percent does not depend on temperature, which is why it is preferred for stock solutions. If you need a volume-based figure, enter the solution density (from a table or a hydrometer reading): the solution volume and the mass concentration in g/L (or % w/v, which is g per 100 mL) follow. Without a density, the volume fields stay empty.

The formula

w = m_solute / (m_solute + m_solvent)

V = m_soln / ρ

γ = m_solute / V = w × ρ

m_solute: mass of solute
m_solvent: mass of solvent
m_soln: mass of solution
w: mass percent (w/w)
ρ: solution density
V: volume of solution
γ: mass concentration (w/v)

Worked example

25 g of sodium chloride is dissolved in 475 g of water. The resulting solution has a density of 1.034 g/mL at 20 °C.

Mass of solution = 25 + 475 = 500 g.
Mass percent = 25 / 500 × 100 = 5.00% w/w.
Volume = 500 / 1.034 = 483.6 mL, so the concentration is 25 g / 0.4836 L = 51.7 g/L.

The brine is 5% NaCl by mass, or 5.17% w/v.

Assumptions and limits

Masses are of the pure substances; for a hydrate salt, the water of crystallization counts towards the solute mass unless you correct for it.
Density is that of the final solution, not the solvent. Volumes are not additive when solutions are mixed.

Frequently asked questions

What is the difference between % w/w and % w/v?

w/w is grams of solute per 100 g of solution; w/v is grams per 100 mL. They are only equal when the density is 1 g/mL.

How do I make 500 g of a 10% solution?

Enter 10% and 500 g of solution: weigh 50 g of solute and add 450 g of solvent.

How is mass percent related to percent composition?

Both are mass fractions. Percent composition describes the share of each element in a compound; the molar mass calculator lists it for any formula.