mg/mL to Molarity Converter
Convert a mass concentration into molarity, or molarity into mg/mL: g/L, mg/mL, µg/mL and ng/mL to M, mM, µM and nM, from the molecular weight.
Calculator
Convert a concentration
Molecular weight in g/mol (Da). For a protein, 25 kDa is 25000.
Enter the formula weight and mass concentration to see the molarity.
Worked example
Normal saline, 0.9% NaCl, in molarity
- 010.9% w/v = 0.9 g in 100 mL = 9 g/L = 9 mg/mL
- 02M = 9 ÷ 58.44
- 03M = 0.154 mol/L
0.9% saline is 0.154 M, or 154 mM, sodium chloride.
How it works
How to convert mg/mL to molarity
Molarity counts molecules; a mass concentration weighs them. One mole of a substance weighs its molecular weight in grams, so dividing grams per litre by grams per mole gives moles per litre.
mg/mL is the same quantity as g/L (a thousandth of a gram in a thousandth of a litre), so mg/mL ÷ MW is mol/L directly. Going the other way, mol/L × MW is g/L, which is again mg/mL.
The smaller units follow the same rule a thousand times smaller on each side: µg/mL ÷ MW is mmol/L, which is 1000 µM, and ng/mL ÷ MW is µmol/L.
Questions
Frequently asked
How do I convert mg/mL to molarity?
Divide the mg/mL by the molecular weight in g/mol: the answer is in mol/L. 9 mg/mL of NaCl (58.44 g/mol) is 9 ÷ 58.44 = 0.154 M.
How do I convert molarity to mg/mL?
Multiply the molarity by the molecular weight. 0.15 M NaCl is 0.15 × 58.44 = 8.77 mg/mL.
How do I convert µg/mL to µM?
Divide by the molecular weight in g/mol and multiply by 1000. 1 µg/mL of glucose (180.16 g/mol) is 1 ÷ 180.16 × 1000 = 5.55 µM.
How do I convert ng/mL to nM?
Divide by the molecular weight in g/mol and multiply by 1000. 50 ng/mL of a 25 kDa protein is 50 ÷ 25000 × 1000 = 2 nM.
Why do I need the molecular weight?
A milligram of a small molecule holds far more molecules than a milligram of a protein. The molecular weight says how many grams one mole weighs, which is what links mass to the number of molecules.
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