Calculator Inputs
Formula Used
Phage titer (PFU/mL) = Average plaque count ÷ (dilution plated × volume plated in mL) × sample preparation factor
For a plate prepared at 10-n, the dilution plated equals 10-n. The reciprocal dilution equals 10n. This calculator averages available replicate counts, applies the plated volume correction, then multiplies by any extra concentration or dilution adjustment entered.
Total batch particles = Titer × total batch volume
Estimated input MOI = (titer × phage input volume × adsorption fraction) ÷ host cell count
How to Use This Calculator
- Enter one to three plaque counts from replicate assay plates.
- Type the positive exponent for the plated dilution, such as 6 for 10-6.
- Enter the plated sample volume in milliliters.
- Add any preparation factor if the plated sample was pre-concentrated or additionally diluted.
- Set the countable plaque range used in your laboratory workflow.
- Optionally add host cells, phage input volume, and adsorption percent for an MOI estimate.
- Press the calculate button to display the results above the form.
- Export the results as CSV or PDF when needed.
Example Data Table
| Replicate | Plaque Count | Plated Dilution | Volume Plated (mL) | Preparation Factor |
|---|---|---|---|---|
| 1 | 145 | 10-6 | 0.10 | 1.00 |
| 2 | 152 | 10-6 | 0.10 | 1.00 |
| 3 | 149 | 10-6 | 0.10 | 1.00 |
This example produces an average plaque count of 148.67 and an estimated titer of 1.49 × 109 PFU/mL.
FAQs
1. What does phage titer mean?
Phage titer expresses the number of plaque-forming units in one milliliter of sample. It estimates the concentration of infectious phage particles capable of producing visible plaques.
2. Why are replicate plates important?
Replicates reduce random counting error and improve reliability. Averaging multiple valid plates usually gives a more stable titer estimate than relying on one plate alone.
3. What plaque range is usually countable?
Many laboratories prefer about 30 to 300 plaques per plate. Counts below the range may be noisy, while higher counts may merge and reduce counting accuracy.
4. What is the dilution exponent field for?
It captures the power of ten used for the plated dilution. Enter 6 when the plated dilution is 10^-6, and the calculator converts it automatically.
5. When should I use a preparation factor?
Use it when the plated material was additionally diluted, concentrated, or otherwise adjusted before assay. Leave the value at 1 when no extra correction is required.
6. Why does volume plated affect titer?
Plaque counts arise from only the plated fraction of the diluted sample. Smaller plated volumes require a correction to estimate the concentration per full milliliter.
7. What is the optional MOI estimate?
It estimates input multiplicity of infection using titer, inoculum volume, adsorption, and host count. It is helpful for planning infections, but depends strongly on accurate host data.
8. Can I export the results for records?
Yes. The calculator includes CSV export for spreadsheet use and PDF export for reports, archiving, validation packages, or routine laboratory documentation.