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PCR Reaction Reagent Volume Calculator

The PCR Reaction Reagent Volume Calculator scales a per-reaction PCR mix into the total reagent volumes needed for a batch. It accounts for the number of reactions and an optional preparation overage, helping you prepare enough master mix without manually multiplying every component.

The calculator is intended for routine laboratory planning where template/sample volume is added separately from shared reaction components. Enter the per-reaction volumes from your validated PCR protocol; the tool does not prescribe reagent concentrations or replace protocol-specific instructions. The main result reports total master-mix volume, while the breakdown shows the batch multiplier and total reaction volume.

Inputs

µL
µL
%
Result
—
Master mix to prepare
Batch multiplier—
Total sample/template volume—
Total combined reaction volume—

1. Confirm the protocol volumes
Use the master-mix and template/sample volumes specified by your established PCR protocol for one reaction.

2. Enter the reaction count
Include samples, controls, standards, and any other wells that require a reaction.

3. Add preparation overage
Use an overage appropriate to your pipetting workflow to cover transfer loss; the calculator does not choose a laboratory policy for you.

4. Review the master-mix volume
The main result scales only the shared master-mix portion by reaction count and overage.

5. Check separate sample volume
The breakdown shows sample/template volume without overage because samples are commonly dispensed individually.

Batch multiplier = Number of reactions × (1 + Overage ÷ 100) Master mix to prepare = Master mix per reaction × Batch multiplier Total reaction volume = (Master mix per reaction + Sample per reaction) × Number of reactions

Where:

  • Number of reactions — all reactions to be set up, including controls as applicable
  • Master mix per reaction — shared reagent volume for one reaction, µL
  • Sample per reaction — template or sample volume added separately, µL
  • Overage — extra master-mix percentage prepared for handling loss

Assumptions: The model assumes a single uniform reaction recipe. It applies overage to the shared master mix only, not to sample/template volume.

What the result means

The batch contains 24 planned 25 µL reactions, while the shared mix is prepared with 10% extra volume to reduce the risk of running short during dispensing.

Use validated assay recipes and laboratory SOPs for actual PCR setup.

Given:

  • 24 reactions
  • 20 µL master mix per reaction
  • 5 µL sample per reaction
  • 10% overage

Calculation:
Batch multiplier = 24 × 1.10 = 26.4 reaction equivalents
Master mix = 20 × 26.4 = 528 µL
Sample total = 5 × 24 = 120 µL

Result:
Prepare 528 µL of master mix

Interpretation:
The batch contains 24 planned 25 µL reactions, while the shared mix is prepared with 10% extra volume to reduce the risk of running short during dispensing.

Does the calculator tell me how much primer, polymerase, or buffer to use?

No. Enter the combined per-reaction master-mix volume from your validated protocol. Individual component concentrations and volumes depend on the assay and reagent system.

Should controls be included in the reaction count?

Include every well or tube that consumes the same master mix, including applicable positive, negative, and no-template controls. This keeps the batch scale aligned with the actual setup.

Why is overage not added to sample volume?

Sample or template is often handled individually and may be limited, so the model only applies overage to the common master mix. If your workflow requires extra sample volume, calculate that separately according to your protocol.

Can I enter a zero sample volume?

Yes, for a workflow where the full reaction is represented by the shared mixture or where sample is accounted for elsewhere. Make sure the resulting per-reaction total still matches the protocol you intend to run.

Is a 10% overage always appropriate?

No. The default is only an editable planning value. Appropriate overage depends on reaction count, pipette characteristics, transfer dead volume, and your laboratory procedure.