How do you calculate the mass needed from molarity?
Molarity is the amount of substance per volume of solution, in moles per litre (M). Since moles = mass ÷ molecular weight, the mass you need is mass (g) = molarity (mol/L) x volume (L) x molecular weight (g/mol). Convert every value to these base units first; the calculator does it for you.
Worked example: a 10 mM stock, 10 mL, of a compound with molecular weight 197.13 g/mol needs 0.010 mol/L x 0.010 L x 197.13 g/mol = 0.0197 g, or 19.71 mg.
How do I make a 10 mM stock solution?
Pick the volume you want, enter the molecular weight from the certificate of analysis, and calculate the mass. If the vial already holds a fixed mass, switch to Volume and enter the mass instead: the calculator gives the volume of solvent that makes 10 mM. Use the batch-specific molecular weight if the compound is a salt or hydrate, because the extra mass changes the result.
How do you convert mg/mL to molarity?
Divide the mass concentration by the molecular weight. 1 mg/mL equals 1 g/L, so for a compound of 500 g/mol, 1 mg/mL ÷ 500 g/mol = 0.002 mol/L, or 2 mM. In the calculator, choose Concentration, enter 1 mg in 1 mL and the molecular weight. To dilute the stock afterwards, use the Dilution Calculator.
Frequently asked questions
What is the formula for molarity?
Molarity (mol/L) = moles of solute ÷ litres of solution, and moles = mass (g) ÷ molecular weight (g/mol). Rearranged: mass (g) = molarity x volume (L) x molecular weight.
How do you make a 1 molar solution?
Dissolve the compound's molecular weight in grams in enough solvent to make 1 litre of solution. For sodium chloride (58.44 g/mol), that is 58.44 g made up to 1 L.
What units is molarity measured in?
Moles per litre, written M. Smaller units are mM (10⁻³ M), µM (10⁻⁶ M), nM (10⁻⁹ M) and pM (10⁻¹² M).
What is the difference between molarity and molality?
Molarity is moles per litre of solution; molality is moles per kilogram of solvent. Lab stock solutions are almost always described by molarity.
Which molecular weight should I use?
The batch-specific value on the certificate of analysis, which accounts for salt forms and water of hydration. The free-base value gives the wrong mass for a salt.
Is anything I enter saved or sent?
No. The calculator runs in your browser. Nothing you type is saved, sent to BioBridgeX or added to the page address, and analytics never see your numbers.
Related free tools
- Dilution Calculator: C1V1 = C2V2 for any unknown, with stock and diluent volumes and the dilution factor.
- Serial Dilution Calculator: Transfer and diluent volumes and a concentration table for 2-fold, 3-fold, half-log or 10-fold series.
- Reconstitution Calculator: Solvent volume to add to a vial of lyophilized protein, antibody or compound for a target stock.
- All lab calculators and every free tool on BioBridgeX.
Sources
Check every result before use. Formulas assume ideal conditions; follow your validated lab procedures and the reagent supplier's instructions. Facts on this page last checked 27 October 2026.
Compare quotes from vetted In Vitro Pharmacology suppliers on BioBridgeX. Free for buyers. Planning is optional: these tools work without an account, and nothing you enter is shared.