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.

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Multiplicity of Infection (MOI) Calculator

MOI from titer/volume/cells or the virus volume for a target MOI, with Poisson % infected. Educational use only.

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2 examples

10⁶ PFU/mL × 1 mL onto 10⁶ cells → MOI 1, 63.21% infected

You infect 1×10⁶ cells in a well with 1 mL of a 1×10⁶ PFU/mL stock. MOI = 1×10⁶ × 1 ÷ 1×10⁶ = 1. By Poisson statistics P(≥1) = 1 − e⁻¹ = 63.21%, so roughly a third of the cells see no virus — fine for spreading infection, too low if every cell must be infected.

{"result":"MOI ≈ 1 → 63.21% of cells infected (P(≥1) = 1 − e^(−MOI)).","metadata":{"result":{"moi":1,"infectedFractionPercent":63.21,"uninfectedFractionPercent":36.79}}}

Target MOI 3 for 2×10⁶ cells at 5×10⁷ PFU/mL → add 120 µL

To reach ~95% infected cells you want MOI 3. For 2×10⁶ cells and a 5×10⁷ PFU/mL stock, the inoculum volume is V = 3 × 2×10⁶ ÷ 5×10⁷ = 0.12 mL = 120 µL; P(≥1) = 1 − e⁻³ = 95.02%.

{"result":"Add ≈ 0.12 mL (120 µL) of stock for MOI 3 → 95.02% of cells infected.","metadata":{"result":{"requiredVolumeMl":0.12,"requiredVolumeUl":120,"moi":3,"infectedFractionPercent":95.02}}}

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6 options

SettingsAdjust formats, ranges, numbers, and modes.6

Calculation ModeselectRequiredCompute MOI from your infection setup, or the virus volume for a target MOI.Viral Titer (PFU/mL)numberRequiredInfectious titer of the viral stock.Infection Volume (mL)numberRequiredVolume of inoculum added to the cells (MOI mode).Cell CountnumberRequiredTotal cells in the well/flask at infection.Target MOInumberRequiredDesired MOI (volume mode); 3 gives ~95% infected cells.Decimal PlacesnumberOptional

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Multiplicity of Infection (MOI) Calculator

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Examples

1. Calculate MOI 1 for one million cells

2. Calculate volume for target MOI 3

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