Calculate mass, molarity, volume, and percent solutions. Built-in reagent library with molecular weights.
mass (g) = Molarity (M) x Volume (L) x MW (g/mol). Select what to solve for:
% w/v = (mass of solute in g / volume of solution in mL) x 100
Convert between molar concentration units. Optionally enter MW to convert to mass concentration (mg/mL).
Click any reagent to load its MW into the molarity calculator.
| Reagent | Formula | MW (g/mol) |
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Molarity (M) is the most common concentration unit in laboratory science, defined as moles of solute per liter of solution. The fundamental relationship connecting mass, molarity, volume, and molecular weight is: mass (g) = Molarity (mol/L) x Volume (L) x Molecular Weight (g/mol). This equation can be rearranged to solve for any unknown when the other three values are known.
Percent solutions are commonly used for reagents where precise molar concentrations are less important. The three types are: % w/v (grams per 100 mL, most common in biology), % v/v (milliliters per 100 mL, used for liquid solutes like ethanol), and % w/w (grams per 100 g total, used in pharmacy and food science).
When preparing solutions, always dissolve the solute in less than the final volume of solvent, then bring to the final volume in a volumetric flask. This ensures accurate final concentration. For temperature-sensitive reagents like Tris, adjust pH at the temperature the buffer will be used, as pKa values shift with temperature.
Use the formula: mass (g) = Molarity (M) x Volume (L) x Molecular Weight (g/mol). For example, to make 500 mL of 1 M NaCl (MW = 58.44): mass = 1 x 0.5 x 58.44 = 29.22 g. Dissolve in ~400 mL water, then top up to 500 mL.
% w/v (weight/volume) = grams of solute per 100 mL of solution — most common in biology labs. % v/v (volume/volume) = mL of liquid solute per 100 mL solution — used for liquids like ethanol, methanol, Tween. % w/w (weight/weight) = grams of solute per 100 g total — used in pharmacy and food science.
mg/mL = Molarity (M) x Molecular Weight (g/mol). For example, 1 mM BSA (MW ~66,500) = 0.001 x 66500 = 66.5 mg/mL. This conversion requires knowing the molecular weight of the solute.
Use the dilution equation: C1 x V1 = C2 x V2. For example, to make 100 mL of 1% SDS from a 10% stock: V1 = (1% x 100 mL) / 10% = 10 mL. Take 10 mL of the 10% stock and add 90 mL water. For more complex dilutions, use our Buffer Calculator.