How It Works
This calculator works in 4 steps.
Enter the requirement
Type the needed volume, or the reaction count and volume per reaction.
Choose the overage method
Select percent (such as 10%) or extra reactions (such as N + 1).
Enter the overage
Type the value from the SOP.
Read the scaled volumes
The calculator returns the total and the per-component volumes with overage.
The Formula
The formula multiplies the requirement by 1 plus the overage fraction, or adds extra reactions.
V_prep = V_need × (1 + o)V_prep = (N + k) × V_rxnΔV = V_prep − V_need- V_need:
- Required volume
- o:
- Overage fraction
- N:
- Reaction count
- k:
- Extra reactions
24 qPCR reactions at 20 µL with 10% overage need 528 µL of master mix. The N + 1 method gives 500 µL.
Conversion Table
The conversion table applies 6 overage levels to required volumes.
| Required volume | Overage | Prepare | Extra volume |
|---|---|---|---|
| 10 mL | 5% | 10.5 mL | 0.5 mL |
| 10 mL | 10% | 11 mL | 1 mL |
| 10 mL | 20% | 12 mL | 2 mL |
| 50 mL | 10% | 55 mL | 5 mL |
| 9.6 mL | 15% | 11.04 mL | 1.44 mL |
| 500 mL | 5% | 525 mL | 25 mL |
What Is the Preparation Overage Calculator?
The Preparation Overage Calculator is a tool that adds a specified excess, as a percent or as a fixed number of extra reactions, to a planned preparation volume. Overage covers pipetting loss, tip retention, and evaporation.
Master mixes are often prepared for N + 1 or N + 10% reactions. The calculator supports both methods and returns the scaled volume of every component. The user sets the overage from the lab's SOP; the calculator applies it and reports the extra volume.
Common Uses
There are 5 main uses of this calculator.
Master mixes
Molecular labs prepare PCR mixes for N + 10%.
Plate reagents
Users prepare detection reagents with overage for reservoirs.
Media batches
Cell culture labs add overage for filter hold-up.
Field batches
Field teams prepare extra for spills and priming.
Production runs
Manufacturers include line losses in batch size.