How this calculator works
This simplified model assumes independent random mixing and equal mask efficacy for source control and recipient protection. The efficacy and uptake values are user assumptions, with no material-based presets. The generation table shows geometric growth without susceptible depletion. It illustrates model sensitivity rather than predicting current COVID-19 cases or personal protection. The result is an estimate for information only and is not medical advice.
Formula
Modelled R = R0 × (1 - efficacy × uptake)^2. New cases in generation g = initial cases × R^g. Inverse product: efficacy × uptake = 1 - sqrt(target R/R0).
Worked example
R0 2.4, efficacy 50% and uptake 50% give 2.4 × 0.75² = 1.35. With 100 initial cases, the next generation is 240 without masks versus 135 in this model.
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Frequently asked questions
Why square the remaining transmission factor?
The model applies the same average reduction to both an infectious source and a susceptible recipient.
Is laboratory filtration efficiency the required input?
Not automatically. Real use includes fit, leakage and adherence. Enter an explicitly assumed overall per-direction efficacy.
Does the table predict an epidemic peak?
No. Geometric growth ignores changing susceptibility and behaviour. The SIR tool adds susceptible depletion.