How to use this calculator
- Enter the target final culture volume.
- Enter stock and desired working concentrations on the same basis.
- Add any preparation overage.
- Calculate the stock and diluent volumes for the batch.
#3279 · Science & Engineering Tool
Bacterial Growth Reagent Volume Calculator
Calculate the stock-reagent volume needed to prepare a target bacterial culture volume at a selected working concentration. The tool applies C1V1 = C2V2, optionally adds preparation overage, and reports both reagent and diluent volumes. Stock and working concentrations may use any matching concentration unit or compatible relative multiples.
Calculator
Laboratory inputsFormula
Stock volume = final volume × (working concentration ÷ stock concentration)
Prepared volume = final volume × (1 + overage %)
Prepared volume = final volume × (1 + overage %)
The stock-volume calculation is applied to the overage-adjusted prepared volume.
What the result means
The main result is the volume of concentrated reagent to add for the full prepared batch. The remaining prepared volume is diluent or culture medium.
Stock and working concentration values must use the same basis. Verify additive volumes, density effects, and protocol-specific order of mixing where material.
Example calculation
To prepare 500 mL at 1× from a 100× stock with 5% overage, prepare 525 mL total. Stock reagent required is 525 × 1 ÷ 100 = 5.25 mL, with 519.75 mL of diluent.
Tips for better results
- Confirm the stock label and concentration unit before use.
- Use calibrated equipment suitable for the calculated volume.
- Check whether the reagent changes final volume appreciably.
- Prepare only the stability-appropriate amount.
- Document lot, concentration, and overage in the batch record.
Frequently asked questions
Can I enter mg/mL instead of an × concentration?
Yes, provided stock and working values use the same concentration unit.
Why is overage applied to both reagent and diluent?
Overage increases the whole prepared batch while preserving the requested final concentration.
What if the working concentration is higher than the stock?
The calculator rejects that setup because dilution cannot create a concentration above the stock.
Does this calculation assume volumes are additive?
Yes. Confirm whether that approximation is suitable for your reagent and protocol.
How do I calculate without preparation overage?
Enter 0% for overage.
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Reagent preparation variables
| Variable | Unit | Meaning |
|---|---|---|
| Final volume | mL | Requested culture batch |
| Stock / working | matching units | Concentration ratio |
| Overage | % | Extra prepared volume |