Incubation Period Distribution Calculator

Work out incubation period distribution instantly with clear inputs, formula shown and shareable results.

About Incubation Period Distribution Calculator

Applies the lognormal incubation model: the chosen percentile is the median multiplied by the exponential of the normal deviate times the log standard deviation.

Formula

Lognormal percentile

Percentile = median x exp(z x sigma), where z is the standard normal deviate for the required percentile

Worked example

With the default values below, Incubation Period Distribution Calculator returns Incubation period at that percentile of 10.482. Change any input above and every figure here is recalculated in your browser.

Inputs used

Median incubation periodaccepts 0.2–60 days: 5 days
Log standard deviationaccepts 0.05–1.5: 0.45
Percentile requiredaccepts 50–99.9: 95

Results

Incubation period at that percentile: 10.482 days
Median used: 5.00 days
Normal deviate applied: 1.645
Rounded quarantine length: 11 days

Step by step

1Values used
2Lognormal percentile
3Incubation period at that percentile= 10.482 days
4Median used= 5.00 days
5Normal deviate applied= 1.645
6Rounded quarantine length= 11 days

Assumptions and limits

The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax or fees or charges into account.
Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Why lognormal?

Incubation periods are right skewed and non-negative, which the lognormal distribution captures well across many infections.

How are quarantine periods set?

Usually at or beyond the 95th to 99th percentile of the incubation distribution.