# Multiplicity of Infection (MOI) Calculator MOI from titer/volume/cells or the virus volume for a target MOI, with Poisson % infected. Educational use only. > Canonical page: https://elysiatools.com/en/tools/moi-calculator - **Category:** Education - **Keywords:** moi calculator, multiplicity of infection, viral titer pfu per cell, virus volume for moi, poisson infection probability, percent cells infected moi, moi 1 63 percent infected, virus infection calculator, cell culture infection, lab calculator ## Overview The Multiplicity of Infection (MOI) Calculator computes MOI from viral titer, infection volume, and cell count, or calculates the virus volume needed for a target MOI. It also estimates the percentage of cells receiving at least one infectious unit using Poisson statistics. For educational use only. ## Inputs - **Calculation Mode** (select): Compute MOI from your infection setup, or the virus volume for a target MOI. - **Viral Titer (PFU/mL)** (number): Infectious titer of the viral stock. - **Infection Volume (mL)** (number): Volume of inoculum added to the cells (MOI mode). - **Cell Count** (number): Total cells in the well/flask at infection. - **Target MOI** (number): Desired MOI (volume mode); 3 gives ~95% infected cells. - **Decimal Places** (number) ## When to use - Calculate MOI for a planned cell infection from PFU/mL, inoculum volume, and cell count. - Determine how much viral stock is needed to reach a target MOI. - Estimate the percentage of cells infected at a selected MOI using Poisson probability. ## How it works - Choose “From titer, volume, and cells” to calculate MOI, or choose “From target MOI and cells” to calculate the required virus volume. - Enter the viral titer in PFU/mL and the total cell count. - Enter the infection volume for MOI mode or the target MOI for volume mode. - The calculator returns MOI, required volume when applicable, and the estimated infected fraction as a percentage. ## Use cases - Planning infections in wells or flasks from a measured viral stock titer. - Calculating viral inoculum volume for a target MOI, such as MOI 3. - Comparing expected infection coverage across different MOI values. ## Frequently asked questions ### What is the MOI formula? MOI is calculated as infectious units divided by cells. With the available inputs, MOI = viral titer × infection volume ÷ cell count. ### How do I calculate virus volume for a target MOI? Use volume mode. The required volume is target MOI × cell count ÷ viral titer. ### What does MOI 1 mean for infection percentage? Under the Poisson model, MOI 1 corresponds to approximately 63.21% of cells receiving at least one infectious unit. ### What percentage of cells are infected at MOI 3? The estimated infected fraction is approximately 95.02%, calculated as 1 − e⁻³. ### What units should I enter? Enter viral titer in PFU/mL, infection volume in mL, and cell count as the total number of cells. ## Related tools - [Peptide Mass Calculator (Monoisotopic/Average)](https://elysiatools.com/en/tools/peptide-mass-calculator): Sums ProtParam residue masses for a peptide sequence (mono or average) and reports M, \[M+H\]⁺, \[M+Na\]⁺, \[M+2H\]²⁺. 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