20
µM
20,000
nM
0.02
mM
20
µM
20,000
nM
0.02
mM
The Protein Molar Conversion calculator converts protein concentration from mass units (mg/mL) to molar units (µM, nM, mM). Many biochemical and biophysical experiments require molar concentrations for proper stoichiometric calculations, binding assays, enzyme kinetics, and drug dosing. This tool provides instant conversion using the molecular weight of your protein, eliminating the need for manual calculation.
The conversion uses the fundamental relationship between mass concentration and molar concentration:
µM = (mg/mL / MW in kDa) × 1000
This works because:
Additional conversions: 1 mM = 1000 µM; 1 µM = 1000 nM
Inputs
Results
1 mg/mL of a 50 kDa protein equals 20 µM. This is a common concentration for enzyme assays and structural studies.
Inputs
Results
0.5 mg/mL of a 150 kDa antibody (IgG) equals approximately 3.33 µM or 3333 nM.
Molar concentration tells you the number of molecules per unit volume, which determines molecular interactions. For example, in a binding assay between a 10 kDa ligand and a 100 kDa receptor, equal mg/mL concentrations give a 10-fold molar excess of the ligand. Molar ratios are essential for understanding stoichiometry, calculating dissociation constants (Kd), and designing titration experiments.
Use the reverse formula: mg/mL = µM × MW(kDa) / 1000. For example, 10 µM of a 50 kDa protein: 10 × 50 / 1000 = 0.5 mg/mL.
Use the molecular weight of the biological unit relevant to your experiment. For a homodimer of 50 kDa subunits, use 100 kDa if measuring the complex, or 50 kDa if measuring monomers. For antibodies: use ~150 kDa for intact IgG, ~50 kDa for Fab fragments, or ~25 kDa for scFv. Always specify whether your concentration refers to the monomer or the complex.
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