Protein Concentration Calculator

Your details

Choose A280 for UV absorbance, standard curve for colorimetric assays, or dilution to find volume or final concentration.
Select a preset to auto-fill extinction coefficient and molecular weight, or choose Custom to enter your own values.
Absorbance reading at 280 nm from your spectrophotometer (dimensionless). For reliable results keep A280 between 0.05 and 1.5.
Optional blank absorbance reading for background correction. Enter 0 if already zeroed on the spectrophotometer.
The molar attenuation coefficient for your protein at 280 nm. Auto-filled from the preset; override for custom proteins.
M⁻¹ cm⁻¹
Cuvette or microvolume cell path length. Standard cuvettes use 1 cm; NanoDrop-style microvolume cells often use 0.1 mm (0.01 cm).
cm
Molecular weight in g/mol (Da). Required to convert molar concentration to mg/mL. Auto-filled from preset.
g/mol
If you diluted the sample before measuring, enter the dilution factor (e.g. 10 for a 1:10 dilution). Use 1 if undiluted.
ConcentrationModerate
1.2739mg/mL

Mass concentration of protein in the original (undiluted) sample

Concentration1.2739µg/µL
Molar concentration19.168µM
Concentration19.168nmol/mL
1.2739 mg/mL
Very dilute<0.1Dilute0.1-1Moderate1-10Concentrated10+

Protein concentration is 1.2739 mg/mL in the original sample.

  • Your A280 reading of 0.840 is within the reliable linear range (0.05-1.5).
  • Molar concentration: 19.17 µM. Useful for stoichiometric calculations, enzyme kinetics, and binding assays.
  • Nucleic acid contamination (DNA/RNA) absorbs at 280 nm and can inflate the reading. A 260/280 ratio near 1.8 (RNA) or 1.9 (DNA) suggests contamination.

Next stepFor highest accuracy, measure a dilution series and confirm linearity, or use a colorimetric method (Bradford, BCA) as a cross-check.

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