How this calculator works
In a simple homogeneous transmission model, the reproduction number scales with the effective contact rate when transmission probability and infectious duration remain constant. This page varies that one factor. A percentage reduction in effective contacts is not a distance in metres and is not directly the percentage of people staying home. The table is a hypothetical geometric comparison. The result is an estimate for information only and is not medical advice.
Formula
R after contact reduction = R0 × (1 - reduction). Reduction to reach R = 1 is max(0, 1 - 1/R0). New cases in generation g = initial cases × R^g.
Worked example
Baseline R 2.5 with a 60% effective-contact reduction gives R 1.0. With 100 initial cases, the next generation is 250 at baseline versus 100 after the assumed reduction.
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Frequently asked questions
Can this choose a safe interpersonal distance?
No. Physical distance, ventilation and exposure duration do not translate into one universal percentage reduction.
Does R = 1 mean no cases?
No. In this simplified generation model, each generation replaces itself at the same size. Decline requires R below 1.
Does the model include immunity?
No. All other factors are held constant. Use a compartmental model when changing susceptibility matters.