Concentration calculator
Find out the molarity of your solution. Enter the molecular weight, the mass of compound and the solvent volume, and the molar concentration is calculated for you.
How the calculation works
The mass you dissolved, divided by the molecular weight, gives the amount of substance in moles. Divide that by the solution volume and you have molarity: C = m / (MW × V). That's all molar concentration is. Enter mass in mg and volume in mL, and the result comes out in mmol/L, usually written mM.
Worked example
Dissolve 5 mg of a compound with MW 342.4 g/mol in 1 mL of DMSO. 5 divided by 342.4 gives 0.0146 mmol, and in 1 mL that makes a 14.6 mM stock. Need exactly 10 mM? Add another 0.46 mL of solvent. The math also runs in reverse for quick checks: a 1 mg/mL solution of the same compound is about 2.9 mM.
Related tools
Know the target concentration and need the weigh-out instead? Use the mass calculator. Have a fixed amount of solid and a target molarity? The volume calculator gives the solvent amount. Molecular weights for every compound we stock are listed on the catalog pages.
Frequently asked questions
How do I convert mg/mL to mM?
Divide the mg/mL value by the molecular weight in g/mol, then multiply by 1000. A 1 mg/mL solution of a compound with MW 400 g/mol is 2.5 mM.
Which molecular weight should I use for a salt form?
The weight of the form on your balance. A hydrochloride salt carries extra mass per mole, so entering the smaller free-base MW makes the result read higher than the solution really is.
Why do screening labs work in molar units rather than mg/mL?
Equal molarity puts the same number of molecules in every well. At equal mg/mL, a compound with half the MW delivers twice the molecules, which skews potency comparisons.
Where do I find the molecular weight of my compound?
Every molecule page in our catalog lists it, and it's included in the downloadable SDF file.