Molarity Calculator

How it works

M = n ÷ V · n = m ÷ MW · m = M × V × MW · V = m ÷ (MW × M) · g/L = M × MW · N = M × equivalents · C₁V₁ = C₂V₂

Molarity is the most common way to state concentration: the number of moles of dissolved solute per litre of the final solution, so a 1 M solution holds one mole in every litre. Choose what you need: the molarity of a solution you made from a known number of moles or a weighed mass, the mass to weigh out for a target concentration (the everyday lab task), or the volume a weighed amount will make. Every field has a unit menu (mol to nmol, kg to µg, L to µL, M to pM) and the result comes back in a sensible unit. Pick a common compound to fill in its molar mass, or choose Other and type it (kDa for proteins). Under More options you can correct for reagent purity and set the equivalents per mole for normality. The results also give mass concentration (g/L, mg/mL), % w/v and, for dilute water solutions, ppm, plus a table for diluting the solution with C₁V₁ = C₂V₂.

Worked example

To make 1 L of 0.5 M NaCl (58.44 g/mol): n = 0.5 mol/L × 1 L = 0.5 mol and m = 0.5 × 58.44 = 29.22 g. Weigh 29.22 g, dissolve it in less than 1 L of water and make up to exactly 1 L. Going the other way, 10 g of NaCl in 0.5 L is 10 ÷ 58.44 = 0.17112 mol, so the molarity is 0.17112 ÷ 0.5 ≈ 0.342 M (342 mM).

Sources: IUPAC Gold Book — amount concentration · PubChem — compound molar masses

Frequently asked questions