Mark Recapture Population Calculator

Work out mark recapture population instantly with clear inputs, formula shown and shareable results.

About Mark Recapture Population Calculator

Applies the Lincoln-Petersen ratio and the less biased Chapman correction to estimate population size from mark and recapture counts.

Formula

Mark-recapture

Lincoln-Petersen: N = M x C / R. Chapman: N = ((M+1)(C+1) / (R+1)) - 1, which is less biased at small sample sizes

Worked example

With the default values below, Mark Recapture Population Calculator returns Chapman population estimate of 379.1. Change any input above and every figure here is recalculated in your browser.

Inputs used

Animals marked and releasedaccepts 1–1,000,000: 60
Animals captured in the second sampleaccepts 1–1,000,000: 80
Marked animals recapturedaccepts 0–1,000,000: 12

Results

Chapman population estimate: 379.1
Lincoln-Petersen estimate: 400.0
Marked share of the second sample: 15.000%
Capture probability per sample: 0.2110

Step by step

1Values used
2Mark-recapture
3Chapman population estimate= 379.1
4Lincoln-Petersen estimate= 400.0
5Marked share of the second sample= 15.000
6Capture probability per sample= 0.2110

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, fees or charges or compounding frequency into account.
Figures are rounded for display to 4 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

What assumptions matter most?

A closed population, equal catchability and marks that neither fall off nor change behaviour.

Why prefer Chapman?

Lincoln-Petersen is biased upward and undefined when no marked animals are recaptured; Chapman remains finite.