Protein Concentration Calculator
Calculate protein concentration from absorbance at 280 nm using extinction coefficient, molecular weight, pathlength, and dilution factor.
This calculator uses the Beer–Lambert-based formula for protein concentration: C = (A / (ε × b)) × m × n, where A is absorbance, ε is the molar extinction coefficient (M⁻¹ cm⁻¹), b is cuvette pathlength (cm), m is molecular mass (g/mol), and n is the dilution factor.
Pick a preset protein or amino acid to auto-fill ε and molecular weight (values for measurements at 280 nm), or choose custom protein and enter your own.
Output can be shown as mg/mL, µg/mL, or ng/mL.
Compute protein concentration from absorbance using C = (A / (ε × b)) × m × n, where A is absorbance (typically at 280 nm), ε is the extinction coefficient (M⁻¹ cm⁻¹), b is pathlength (cm), m is molecular mass (g/mol), and n is the dilution factor.
ε = 210,000 M⁻¹ cm⁻¹ · MW = 150,000 g/mol (280 nm)
For most proteins, measure at 280 nm.