What's the Risk?

"1 in 10,000" and "1 in a million" both just sound rare, even though one is a hundred times the other. This tool turns risk numbers into squares you can see and compare, a vaccine against the disease it prevents, or either one against everyday risks like a car crash or a lightning strike. Pick a comparison below, or build your own.

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Serious outcome Mild or transient outcome

How to read this

The gray area represents 100,000 people in the relevant population, shown by the color-coded age band atop each chart. Each colored square is sized so its area equals the number affected, so very rare risks appear as tiny specks and common outcomes as larger blocks. Comparisons are most reliable within the same population. When two charts cover different age groups or timeframes, treat the comparison as a rough sense of scale rather than a precise apples-to-apples number. Rates are annual unless otherwise noted. Hover or tap any square for details and a link to the data source.