wikiHow Calculating the Concentration of a Solution Calculator To calculate the concentration of a solution, you need to know the amount of solute (the substance being dissolved) and the amount of solvent (the substance doing the dissolving). Concentration can be expressed in different units, such as mass per volume (e.g. g/L), moles per volume (e.g. mol/L), or percent by mass/volume (e.g. % w/v). Here are some common formulas for calculating concentration: Mass per volume (e.g. g/L): concentration = mass of solute / volume of solution Moles per volume (e.g. mol/L): concentration = moles of solute / volume of solution Percent by mass/volume (e.g. % w/v): concentration = (mass of solute / volume of solution) x 100 For example, let's say you dissolve 10 grams of salt (NaCl) in 500 milliliters of water. To calculate the concentration in g/L, you would use the formula: concentration = mass of solute / volume of solution concentration = 10 g / 0.5 L concentration = 20 g/L So the concentration of the salt solution is 20 g/L. Page