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Protein Assay Dilution Factor Estimator

The Protein Assay Dilution Factor Estimator determines the fold dilution created when a sample aliquot is combined with diluent, and it can convert a concentration measured in that diluted sample back to the original sample concentration. It is useful when protein samples must be brought into an assay's working range before reading a standard curve.

Enter the sample volume, diluent volume, and, optionally, the concentration determined for the diluted sample. The calculator reports the total dilution factor and the corresponding original concentration estimate. This page treats the dilution as a simple volume ratio; it does not account for non-additive volumes or assay-specific matrix effects.

Dilution inputs

µL
µL
mg/mL
Result
—
Total dilution factor
Total diluted volume—
Estimated original concentration—
Sample fraction—

1. Enter the protein-sample aliquot
Use the volume of original sample taken before dilution.

2. Enter diluent volume
Provide the volume added to that aliquot using the same unit.

3. Optionally enter the diluted concentration
If the assay has already produced a concentration for the diluted sample, enter it to estimate the original concentration.

4. Review the fold dilution
A 10× result means the original sample represents one tenth of the final diluted volume.

5. Use the corrected concentration
Multiply the diluted concentration by the reported factor when reporting the original sample concentration, provided the dilution model is appropriate.

Total volume = sample volume + diluent volume

Dilution factor = total volume / sample volume

Original concentration = measured diluted concentration × dilution factor

Where:

  • Sample volume and diluent volume must use the same volume unit.
  • Measured diluted concentration is entered in mg/mL.
  • Dilution factor is dimensionless.

Assumptions: Volumes are treated as additive and the diluted sample is assumed to be well mixed.

What the result means

The main result is the fold dilution produced by the entered sample and diluent volumes.

The concentration correction is valid only if the assay response for the diluted sample is within an appropriate quantitative range.

Given:

  • Sample = 15 µL
  • Diluent = 135 µL
  • Measured diluted concentration = 0.62 mg/mL

Calculation:
Total volume = 15 + 135 = 150 µL
Dilution factor = 150 / 15 = 10
Original concentration = 0.62 × 10 = 6.2 mg/mL

Result:
10× dilution; estimated original concentration = 6.2 mg/mL

The diluted assay result is multiplied by ten to express the concentration before dilution.

Is a 1:10 dilution entered as 10×?

If one part sample is present in ten parts total volume, the total dilution factor is 10×. For example, 20 µL sample plus 180 µL diluent gives 200/20 = 10.

Can the sample and diluent volumes use different units?

No. Convert them to the same unit before entering values; the factor itself is unitless because it is a volume ratio.

What happens if I enter zero diluent?

The dilution factor becomes 1×, meaning the sample is undiluted. The measured and original concentrations are then the same.

Can I use this for serial dilutions?

For multiple dilution steps, calculate the factor for each step and multiply the factors. This page models one combined sample-plus-diluent step.

Why might the corrected concentration still be unreliable?

A correct arithmetic dilution factor cannot fix an assay reading outside its quantitative range or matrix effects that change assay response. Validate the diluted measurement itself before back-calculating.