What this is for: Virus titer from plaque counts — one row per dilution (10⁻¹–10⁻⁸) with triplicates, countable-range flags, and a suggested dilution for the headline titer.
The formula: PFU/mL = mean plaques ÷ (dilution × volume plated in mL)
How to use:
- For each dilution from 10^-1 to 10^-8, enter the 3 replicate plaque counts and the volume plated in mL.
- Check the per-dilution table for the mean, PFU/mL, and the 10–100 countable flag.
- Choose the countable dilution by entering its exponent as the chosen dilution.
- Read the headline titer in PFU/mL, its log₁₀ titer, and the approx. TCID50/mL equivalent.
Plaque Assay — PFU/mL Calculator (corrected structure)
The dilution series starts at 10^-1 and runs down to 10^-8, with 3 replicate plaque counts at each dilution. Per dilution: mean plaque count, implied PFU/mL = mean ÷ (dilution × volume plated), and the 10–100 countable-range flag applied to the mean. The headline titer comes from the chosen countable dilution.
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HEADLINE TITER — PFU/mL (from chosen dilution)
log10 titer (from headline titer)
Approx. TCID50/mL equivalent (PFU/mL / 0.69)
Mean PFU/mL over countable dilutions (mean in 10–100)
| Dilution | Volume (mL) | Replicates | Mean plaques | SD | PFU/mL | Countable? (10–100) |
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Prefer to work offline or keep a copy? The download link is right below.
Download the Plaque Assay PFU Calculator workbook (.xlsx)
Download the Plaque Assay PFU Calculator workbook (.xlsx)
Notes & limits (from the workbook): PFU/mL = plaques ÷ (dilution × volume plated). Counts outside the 10–100 countable range (applied to the replicate mean at each dilution) are flagged and should be excluded. The headline titer is taken from the chosen countable dilution — in the worked example the 10^-6 dilution (replicates 38, 42, 40; mean 40 plaques; 0.5 mL plated) gives 40 ÷ (10^-6 × 0.5) = 8.0e7 PFU/mL. The TCID50 equivalent uses the approximate PFU ÷ 0.69 conversion.