Solution Prep Calculator

In short: Calculate required solute mass for target molarity and final solution volume. It is free, works in your web browser and needs no download.

Calculate required solute mass from target molarity, molecular weight, and final solution volume.

How much solute to weigh

To make a solution of a target molarity, weigh mass (g) = molarity (mol/L) × final volume (L) × molecular weight (g/mol). Example: 250 mL of 0.1 M NaCl (58.44 g/mol) needs 0.1 × 0.250 × 58.44 = 1.461 g.

Dissolve the solute in less solvent than you need, then make it up to the final volume in a volumetric flask. If your reagent is a hydrate, use the molecular weight of the hydrate form.

Working in millimolar: divide by 1000 first, so 50 mM is 0.050 M. Example: 500 mL of 50 mM glucose (180.16 g/mol) needs 0.050 × 0.500 × 180.16 = 4.50 g. Use an analytical balance for small masses, and record the exact mass weighed so you can calculate the true concentration afterwards.