Biology
Protein Concentration (A280) Calculator
Estimate protein concentration from a 280 nm absorbance reading using the Beer–Lambert relationship.
Your inputs
Change any value to update the result instantly.
Protein concentration
0.8 mg/mL
Concentration
800 µg/mL
Dilution factor applied
1 ×
Extinction coefficient used
1 (mg/mL)⁻¹cm⁻¹
E⁰·¹% is protein-specific and depends on tryptophan/tyrosine content (e.g. IgG ≈ 1.4, BSA ≈ 0.67). Use the value computed from your protein's sequence for accuracy.
What this calculator does
Estimates protein concentration from A280 absorbance using the Beer–Lambert relationship.
What your result means
Concentration in mg/mL after applying the extinction coefficient and dilution factor.
Formula and working
concentration (mg/mL) = (A280 × dilution) ÷ E⁰·¹% — the absorbance of a 1 mg/mL solution
- 1
Collect the inputs
Absorbance at 280 nm = 0.8 A280; E⁰·¹% extinction coefficient = 1 (mg/mL)⁻¹cm⁻¹; Dilution factor = 1 ×
- 2
Apply the formula
concentration (mg/mL) = (A280 × dilution) ÷ E⁰·¹% — the absorbance of a 1 mg/mL solution
- 3
Result
Protein concentration = 0.8 mg/mL
Frequently asked questions
Symbols and assumptions
- A280
- Absorbance at 280 nm
- E⁰·¹%
- Absorbance of a 1 mg/mL solution in a 1 cm cell
- c
- Concentration = A280 × dilution ÷ E⁰·¹%
- • A 1 cm path length.
- • The E⁰·¹% value entered is correct for the protein being measured.
Sources and review
Reviewed 2026-09-22 · Next review 2027-09-22
- • Proteins with few aromatic residues absorb weakly at 280 nm; nucleic-acid contamination inflates the reading.
Important limitation
This is an educational estimate based only on the values and formula shown. Verify current rates, rules, units, and professional standards before relying on the result. It is not personalized financial or investment advice.
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