Volume calculator
Find out how much solvent to add. Enter the molecular weight, the mass of compound and the target molar concentration, and the required volume is calculated for you.
How the calculation works
The mass divided by the molecular weight gives the amount of substance in your vial. Divide that by the target concentration and you get the volume that hits it exactly: V = m / (MW × C). Enter mass in mg, MW in g/mol and concentration in mM; the result comes back in mL.
Worked example
You have 3 mg of a compound with MW 300 g/mol and want a 10 mM stock. 3 / (300 × 0.01) = 1, so dissolve it in exactly 1 mL. Smaller amounts follow the same route: 2 mg of a compound with MW 750 g/mol at a 5 mM target needs 0.53 mL, which is 533 µL.
Related tools
Starting from a target volume instead? The mass calculator gives the weigh-out. Solution already made and you want its molarity? Use the concentration calculator. The MW of anything we stock is on its catalog page.
Frequently asked questions
The compound won't dissolve at the calculated volume. What can I do?
You've hit its solubility limit. Sonicate or warm the vial gently, or lower the target concentration. DMSO dissolves most screening compounds at 10 mM.
The result is a fraction of a milliliter. How do I measure that?
1 mL is 1000 µL, so 0.53 mL is 530 µL. Volumes under about 10 µL are hard to pipette accurately; scale both mass and volume up instead.
Does the choice of solvent change the calculation?
No. Molarity counts moles per liter of solution whatever the solvent. Only solubility differs between DMSO, water or buffer.
Can I trust the mass printed on a pre-weighed vial?
Within its stated tolerance. For dose-response work, reweigh the solid or correct for the purity and salt data on the certificate of analysis.