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Protein Assay Sample Capacity Estimator

The Protein Assay Sample Capacity Estimator calculates how many complete assay reactions can be supported by an available amount of sample when each reaction consumes a fixed sample volume. A reserve percentage can be withheld for repeat measurements, handling loss, or another planned use.

This is useful when deciding plate layout, replicate count, or whether a limited protein sample can support a planned assay. The calculator reports the usable sample volume after reserve, the maximum whole reaction count, and the leftover usable volume. It is a volume-based planning tool; concentration requirements and assay detection limits must be evaluated separately.

Sample planning inputs

µL
µL
%
Result
—
Complete assay reactions supported
Usable sample—
Usable sample remaining—
Reserved sample—

1. Enter available sample
Use the volume that can be allocated to this assay before the reserve is applied.

2. Set sample volume per reaction
Enter the aliquot consumed by one well or tube, not the working-reagent volume.

3. Choose a reserve percentage
Hold back sample for repeats, confirmatory work, dead volume, or other planned needs.

4. Review complete-reaction capacity
The result rounds down to the number of reactions that can each receive the full sample aliquot.

5. Inspect remaining sample
The breakdown separates the planned reserve from the small usable leftover after whole reactions are allocated.

Reserved sample = available sample × reserve %

Usable sample = available sample − reserved sample

Reaction capacity = floor(usable sample / sample per reaction)

Leftover = usable sample − reaction capacity × sample per reaction

Where:

  • Volumes are in µL.
  • Reserve % is converted to a decimal before multiplication.
  • floor means only complete reactions are counted.

Assumptions: Every reaction is assumed to consume the same sample volume. This does not determine whether the sample concentration is sufficient for the assay.

What the result means

The main result is the maximum number of complete assay reactions supported after the specified sample reserve is held back.

Include replicate and repeat strategy in your planning; do not count the reserved portion as immediately available for routine wells.

Given:

  • Available sample = 430 µL
  • Sample per reaction = 8 µL
  • Reserve = 12%

Calculation:
Reserved = 430 × 0.12 = 51.6 µL
Usable = 430 − 51.6 = 378.4 µL
Capacity = floor(378.4 / 8) = 47 reactions
Leftover = 378.4 − 47 × 8 = 2.4 µL

Result:
47 complete reactions, with 2.4 µL usable sample remaining

An additional 51.6 µL is intentionally held outside the routine reaction allocation.

Does the per-reaction value include assay reagent?

No. Enter only the sample volume consumed per reaction. Use a reagent-volume calculator separately for working reagent.

Should I count standards against sample capacity?

Standards prepared from separate standard material do not consume the unknown sample. Count only reactions that use this available protein sample.

Why is the reserve removed before calculating capacity?

The reserve is intentionally unavailable to routine reactions. Removing it first prevents the displayed capacity from depending on volume you wanted to protect.

Can I plan replicates with this result?

Yes. Divide the supported reaction count by the number of replicates per condition to estimate how many conditions can fit, while accounting separately for controls and other wells.

What if concentration, not volume, is the limiting factor?

This calculator will not detect that. Check the assay input mass or concentration requirements and adjust the sample volume or dilution plan accordingly.