TCID50 Guide
TCID50 to PFU Conversion: Why It Is Only an Estimate
Why TCID50 to PFU conversion is a rough estimate and how to use it carefully when comparing viral titer results.
TCID50 and PFU Are Different Readouts
TCID50 measures the dilution that infects 50 percent of test units. PFU counts plaque-forming units under plaque assay conditions. They are related measures of infectious virus, but they are not the same assay.
Why the Conversion Is Approximate
A common TCID50 to PFU estimate uses a Poisson-based relationship, but the result depends on cell line, virus, endpoint scoring, inoculation volume, and assay conditions. Treat the number as a planning estimate, not a validation result.
Safer Use
Use the estimate to sanity-check a viral titer or plan a rough dilution. For reporting or comparing experiments, prefer the assay-specific value and method used by the protocol.