# Bradford Assay Calculator (BSA Standard Curve) Least-squares BSA curve, back-calculated unknowns with dilution factor, extrapolation flags, and protein-specific dye-response caveats. Educational use only. > Canonical page: https://elysiatools.com/en/tools/bradford-assay-calculator - **Category:** Education - **Keywords:** bradford assay calculator, protein quantification a595, coomassie brilliant blue assay, bsa standard curve, protein concentration from absorbance, standard curve linear regression protein, bradford protein assay protocol, unknown sample protein concentration, microplate protein assay, biochemistry calculator, lab calculator ## Overview The Bradford Assay Calculator fits a least-squares BSA standard curve from concentration and A595 data, then back-calculates unknown protein concentrations with the selected dilution factor. Results include the curve slope, intercept, R², concentration in µg/mL and mg/mL, plus flags for extrapolated readings. Educational use only. ## Inputs - **Protein Standards (µg/mL, A595)** (textarea): One standard per line: concentration in µg/mL, then A595 (comma, semicolon, tab, or space separated). - **Unknown Absorbances (A595)** (textarea): One sample A595 reading per line (blank-subtracted readings are fine as long as the curve includes the blank). - **Sample Dilution Factor** (number): Dilution applied to the sample before the assay (1 = undiluted). - **Decimal Places** (number) ## When to use - Quantify unknown protein samples from Bradford assay A595 readings. - Convert absorbance readings into sample concentrations using a BSA standard curve. - Check curve fit quality and identify unknowns measured outside the standard range. ## How it works - Enter one BSA standard per line as concentration in µg/mL followed by A595, separated by a comma, semicolon, tab, or space. - Enter one unknown sample A595 reading per line and provide the sample dilution factor. - The calculator fits a least-squares line and reports the slope, intercept, and R² value. - It solves the curve for each unknown, applies the dilution factor, and returns concentrations with the selected decimal places. ## Use cases - Teaching standard-curve fitting and protein quantification in biochemistry courses. - Estimating protein concentration in lysates or other unknown samples from microplate A595 readings. - Comparing diluted sample results with the fitted BSA calibration range. ## Frequently asked questions ### What data should I enter for the standards? Enter one standard per line as concentration in µg/mL followed by its A595 reading, such as 10, 0.200. ### What does the dilution factor do? It converts the concentration measured in the diluted assay sample back to the original sample concentration. Use 1 for an undiluted sample. ### What equation is used for unknowns? The calculator inverts the fitted line using c = (A − b) / m, then applies the dilution factor. ### What does an extrapolation flag mean? It means the unknown absorbance falls outside the absorbance range covered by the entered standards. ### Can this calculator be used for clinical or diagnostic decisions? No. It is intended for education and experiment planning, not clinical or diagnostic use. ## Related tools - [BCA Assay Calculator (Protein Standard Curve)](https://elysiatools.com/en/tools/bca-assay-calculator): Least-squares A562 curve fit, back-calculated unknowns with dilution factor, extrapolation flags, and detergent/reducing-agent compatibility notes. 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