Protein Assay Concentration Calculator

1. Enter the processed sample signal
Use the signal value appropriate to your fitted standard curve, after any protocol-required blank or background handling.

2. Enter the fitted slope
Provide the slope from a linear standard curve expressed as signal per mg/mL.

3. Enter the intercept
Use the intercept from the same fitted line rather than forcing it to zero unless that is how the curve was intentionally modeled.

4. Apply the dilution factor
Enter the total fold dilution used before the sample was measured; use 1 for no dilution.

5. Check both concentrations
The breakdown shows concentration in the measured diluted sample, while the main result reports the back-calculated original concentration.

Standard curve: signal = slope × concentration + intercept

Measured concentration = (signal − intercept) / slope

Original concentration = measured concentration × dilution factor

Where:

• Signal = processed assay response in arbitrary units (AU).
• Slope = AU per mg/mL for the fitted linear standard curve.
• Intercept = AU at zero concentration according to the fit.
• Dilution factor = total fold dilution before measurement.

Assumptions: The fitted relationship is assumed to be linear and applicable to the sample signal. The sample and standards should be handled consistently.

What the result means

The main result estimates protein concentration in the original sample before the entered dilution.

Do not extrapolate far beyond the standard-curve range; use the fitting model specified by the assay method when it is not linear.

Given:

• Signal = 0.74 AU
• Slope = 0.36 AU/(mg/mL)
• Intercept = 0.02 AU
• Dilution factor = 4

Calculation:
Net signal = 0.74 − 0.02 = 0.72 AU
Measured concentration = 0.72 / 0.36 = 2.0 mg/mL
Original concentration = 2.0 × 4 = 8.0 mg/mL

Result:
8.0 mg/mL

The measured aliquot corresponds to 2.0 mg/mL, and the fourfold dilution correction returns an estimated 8.0 mg/mL in the original sample.