Calculate the Concentration of a Solution

Updated 4 November 2026 · Standard formula, shown below

Mass concentration 23.40 g/L

Amount of solute: 0.1001 mol; Result
Molarity: 0.4004 mol/L; Result
Percent weight per volume: 2.34 % w/v; Result

This calculator finds the concentration of a solution from the mass of solute you dissolve and the final volume of the solution. Add the molar mass of the solute and you also get the moles and the molarity.

Formula

Mass concentration = m ÷ V. Moles n = m ÷ M. Molarity c = n ÷ V, with V in litres. Percent w/v = grams of solute per 100 mL of solution = m ÷ V(mL) × 100.

m: mass of solute in grams
M: molar mass in g/mol (sum of the atomic masses in the formula)
V: final volume of the solution in mL (divided by 1000 for litres)

Worked Example

5.85 g of sodium chloride (M = 58.44 g/mol) made up to 250 mL.

V = 250 ÷ 1000 = 0.250 L; mass concentration = 5.85 ÷ 0.250 = 23.40 g/L
n = 5.85 ÷ 58.44 = 0.1001 mol
Molarity = 0.100103 ÷ 0.250 = 0.4004 mol/L
Percent w/v = 5.85 ÷ 250 × 100 = 2.34%

Limits and common mistakes

V is the final volume of the solution, not the volume of water you added; dissolving a solid changes the volume.
Keep millilitres and litres apart: forgetting the ÷ 1000 makes the molarity 1000 times too small.
Molarity changes slightly with temperature because the volume does. For a mass-based measure use molality.

Formula used

in m | Mass of solute | g | 5.85 | 0
in mw | Molar mass of the solute | g/mol | 58.44 | 0
in v | Final volume of solution | mL | 250 | 0
out gl | Mass concentration | g/L | m / (v / 1000) | 2
out mol | Amount of solute | mol | m / mw | 4
out molar | Molarity | mol/L | mol / (v / 1000) | 4
out pct | Percent weight per volume | % w/v | m / v * 100 | 2

Each line is one input (in, sel, list) or one result (out: label, unit, formula, decimals). How the calculators work

Method: the standard formula for this calculation, rounded as each result states. See how the calculators work or report an error.