BCA Assay Calculator

The BCA Assay Calculator converts your colorimetric absorbance reading into a precise protein concentration using your BSA standard curve — no manual linear equation solving needed. Enter your sample absorbance at 562 nm, standard curve slope and intercept, and dilution factor to get your protein concentration in mg/mL. Secondary outputs include concentration in µg/µL, g/L, and — if you provide the protein molecular weight — molar concentration in µM.

AU

Absorbance reading of your sample at 562 nm

AU

Background absorbance to subtract from sample

AU/(mg/mL)

Slope of your BSA standard curve

AU

Y-intercept of your standard curve

Factor by which sample was diluted before assay

Da

For molar concentration conversion

Results

Protein Concentration

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Protein Concentration

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Protein Concentration

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Molar Concentration

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Frequently Asked Questions

What is the BCA assay and how does it work?

The BCA (Bicinchoninic Acid) assay is a colorimetric method for protein quantification. Proteins reduce Cu²⁺ to Cu¹⁺ in alkaline conditions, and BCA chelates with Cu¹⁺ to produce a purple complex that absorbs at 562 nm. The absorbance is proportional to protein concentration.

Why do I need a standard curve for BCA assay?

A standard curve using known concentrations of BSA (Bovine Serum Albumin) establishes the relationship between absorbance and protein concentration. This allows you to determine unknown sample concentrations by interpolation.

What dilution factor should I use?

The dilution factor depends on your expected protein concentration. For concentrated samples (>2 mg/mL), dilute 1:10 or more to stay within the linear range of the assay. Always account for this dilution in your final calculation.

How do I handle blank correction in BCA assay?

Measure a blank containing all reagents except protein (use buffer instead). Subtract the blank absorbance from all readings to correct for background interference and reagent color.

What factors can interfere with BCA assay accuracy?

Common interferents include reducing agents (DTT, TCEP), chelating agents (EDTA), and high concentrations of detergents. Lipids, nucleic acids, and some buffer components can also affect results.

What is the typical detection range for BCA assay?

The BCA assay typically works in the range of 20-2000 µg/mL (0.02-2 mg/mL) with good linearity. The microplate version can detect as low as 5 µg/mL, while the tube version works best above 20 µg/mL.

How do I convert between different protein concentration units?

Common conversions: 1 mg/mL = 1000 µg/mL = 1 µg/µL = 1 g/L. For molar units, divide by molecular weight: µM = (mg/mL × 1000) / MW(Da). This calculator performs all conversions automatically.

What should I do if my sample reading is outside the standard curve range?

If absorbance is too high, dilute your sample further. If too low, concentrate your sample or use a more sensitive assay. Always ensure readings fall within the linear portion of your standard curve for accurate results.