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Protein Concentration from A280 Calculator — result sheet
Estimate protein concentration from a corrected 280 nm absorbance, path length, dilution factor, and protein-specific 0.1% extinction coefficient.
Inputs used
Results
Visual chart
Breakdown
Calculation steps
Returned data table
Formula and methodology
Formula: Corrected A280 = measured A280 − blank A280. Concentration in mg/mL = corrected A280 × dilution factor ÷ (extinction value for 1 mg/mL × path length). g/L has the same numerical value as mg/mL. Molarity in μM = concentration in g/L ÷ molecular weight in g/mol × 1,000,000.
The A280 method is a transparent absorbance calculation whose coefficient depends on the protein and measurement conditions. The page requires the visitor to provide the protein-specific coefficient rather than pretending that one coefficient is universal.
This result follows the calculator's declared inputs, precision, validation boundaries, and model limits.
Input contract
- Measured A280 — AU; minimum 0; maximum 100
- A280 blank correction — AU; minimum 0; maximum 100
- Dilution factor — ×; minimum 1.0E-6; maximum 1000000
- Optical path length — cm; minimum 1.0E-6; maximum 100
- A280 of 1 mg/mL protein — A per mg/mL; minimum 1.0E-6; maximum 1000
- Protein molecular weight — Da; minimum 1.0E-6; maximum 100000000
Worked example
| Input | Value |
|---|---|
| Measured A280 | 0.7 |
| A280 blank correction | 0 |
| Dilution factor | 10 |
| Optical path length | 1 |
| A280 of 1 mg/mL protein | 1.4 |
| Protein molecular weight | 150000 |
The corrected A280 is 0.7, the estimated original concentration is 5 mg/mL, and the corresponding concentration is about 33.333 μM for a 150,000 Da protein.
Assumptions and limits
- A280 and the blank are measured at the same wavelength and under the same optical conditions.
- The blank is subtracted once before the dilution correction is applied.
- The entered extinction value describes the absorbance of 1 mg/mL of this protein under the stated path-length convention.
- The dilution factor is the ratio that converts the measured diluted sample back to the original sample.
- The path length is measured in centimetres and is included linearly.
- Molecular weight in daltons is used numerically as grams per mole for the molarity conversion.
- The sample obeys the linear absorbance relationship over the measured range.
- Scattering, contaminants, aggregation, nucleic-acid interference, and instrument saturation are not corrected automatically.
- The page does not select an assay, standard curve, buffer, wavelength, or safety procedure.
- Laboratory quality control and the method validated for the specific sample control the final reported concentration.
Calculator note
Source and methodology
Use the official WorldCalculate methodology policy for the source, formula, precision, and boundary standards behind this calculator.
Planning estimate, not financial, medical, legal, or professional advice. © WorldCalculate — reuse with attribution. Built and curated by Hassan ALRowaie.
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