Calculate the ratio of infectious agents (viruses, phages) to target cells for optimal viral infection experiments and research protocols.
MOI (Multiplicity of Infection)
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Total Infectious Units
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Infection Probability
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Uninfected Cells (%)
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Multiple Infection (%)
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MOI is the ratio of infectious agents (viruses, phages) to target cells in a defined volume. It represents the average number of viral particles that could potentially infect each cell. For example, MOI = 1 means there's an average of 1 virus per cell.
Use the titer that represents functional, infectious units for your specific system. PFU (plaque-forming units) for bacteriophages, TU (transducing units) for lentiviruses, or IFU (infectious units) for other viral systems. Avoid using genome copies (vg/mL) as they don't represent infectious particles.
The relationship follows Poisson statistics. At MOI = 1, approximately 63% of cells get infected. At MOI = 0.3, about 26% of cells are infected, while at MOI = 3, about 95% are infected. Higher MOI increases infection rate but also increases multiple infections per cell.
It's not recommended. Genome copies include non-infectious particles, leading to overestimated MOI values. Always use functional titers (PFU, TU, IFU) that represent actual infectious capacity for accurate MOI calculations.
MOI 0.3 corresponds to approximately 26% infection rate according to Poisson distribution. This is often used when you want single infections with minimal multiple infections per cell, common in clonal selection experiments.
MOI is a guide based on theoretical models. Actual outcomes depend on experimental conditions, cell state, viral stability, adsorption efficiency, and assay methods used for titer determination. Always validate with pilot experiments.
For volumes smaller than minimum pipettable amounts (typically 0.5-1 μL), consider serial dilutions or prepare larger volumes for multiple experiments. The calculator shows when volumes become impractical for standard pipetting.
Theoretical MOI is calculated from input values assuming perfect conditions. Actual MOI accounts for factors like viral adsorption efficiency, cell viability, and time-dependent viral decay. The theoretical calculation provides a starting point for optimization.