mg/mL to Molarity Calculator
Convert a concentration in mg/mL to molarity (mol/L and mM) — or go the other way — using the molecular weight. Switch direction with one click; the math runs instantly in your browser.
Enter the molecular weight to see the result.
How to convert between mg/mL and molarity
A concentration in mg/mL tells you the mass of solute per millilitre, while molarity (M, mol/L) tells you how many moles of solute sit in each litre. The link between them is the molecular weight (MW), in grams per mole.
The conversion is simple once you notice that 1 mg/mL = 1 g/L. Molarity is grams per litre divided by the molar mass, so:
Rearranging gives the reverse conversion, which lets you turn a target molarity back into a mass-per-volume concentration:
Worked example
Suppose you have 2 mg/mL of a compound whose molecular weight is 180 g/mol. Then M = 2 ÷ 180 = 0.0111 M, which is the same as 11.1 mM. Going the other way, 0.0111 M × 180 g/mol returns 2 mg/mL.
Related tools
- Need molarity from a mass and volume? Use the molarity calculator.
- Diluting a stock to a lower concentration? Use the dilution calculator.
Frequently asked questions
›How do I convert mg/mL to molarity?
Divide the concentration in mg/mL by the molecular weight (MW) in g/mol. Because 1 mg/mL equals 1 g/L, the result is in mol/L (molar). For example, 2 mg/mL of a 180 g/mol compound is 2 ÷ 180 = 0.0111 M, or 11.1 mM. Enter both values above and the calculator does this instantly.
›What is the mg/mL to molarity formula?
Molarity (M) = (concentration in mg/mL) ÷ (molecular weight in g/mol). To go the other way, mg/mL = molarity (M) × molecular weight (g/mol). The conversion works because a milligram per millilitre is the same as a gram per litre, and molarity is just grams per litre divided by grams per mole.
›Why do I need the molecular weight?
mg/mL is a mass-per-volume concentration, while molarity counts the number of moles per litre. The molecular weight (g/mol) is the bridge between mass and moles, so you cannot convert between the two without it. Use the formula weight printed on the reagent bottle or from a chemistry database.
›Is this mg/mL to molarity calculator free?
Yes. This converter is completely free, runs entirely in your browser, needs no sign-up, and never sends your numbers to a server.
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