How to use the herd immunity threshold calculator
Find the share of a population that must be immune to stop an infection spreading, from its basic reproduction number. Enter basic reproduction number in the field above; the herd immunity threshold, herd immunity threshold as fraction are computed instantly and plotted on the chart so you can see how the answer changes.
Common searches this calculator answers include “herd immunity threshold”, “R0 vaccination coverage”, “herd immunity percent”, “calculate herd immunity threshold”, “find herd immunity threshold”.
Formula
Variables
- R0 — Basic reproduction number
Worked example
With basic reproduction number = 4, the calculator gives herd immunity threshold ≈ 75 %; herd immunity threshold as fraction ≈ 0.75 fraction.
Frequently asked questions
What is the herd immunity threshold calculator used for?
Find the share of a population that must be immune to stop an infection spreading, from its basic reproduction number. It helps with questions such as “herd immunity threshold”, “R0 vaccination coverage”, “herd immunity percent”.
What is the formula for the herd immunity threshold calculation?
Herd immunity threshold (%) = (1-1 / R0) × 100. Herd immunity threshold as fraction (fraction) = 1-1 / R0. Here R0 is basic reproduction number.
What inputs do I need for the herd immunity threshold calculator?
You need basic reproduction number. Each field is pre-filled with a typical example so you can see how the result responds as you edit the numbers.
How do I use the herd immunity threshold calculator?
Type values into the input fields. Results and the chart update instantly. Use Reset to restore the example values, Copy results to paste them elsewhere, or Share to copy a link that preserves your inputs.
Is the herd immunity threshold result exact?
Calculations use standard formulas and double-precision arithmetic, then display about seven significant figures. Real-world measurements carry uncertainty, so treat results as estimates unless your inputs are exact.