Ecology & populations · SL/HL

Lincoln index

Estimate population size from capture and recapture.

Your values

Number formats & units

Use decimal dots in datasets. Single values also accept decimal commas and scientific notation such as 1.2e-3 or 1.2 × 10⁻³.

Calculated locally. No account or input upload.

Example

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N=\frac{n_1n_2}{n_3}

What the variables mean

Symbol	Meaning
$n_{1}$	Number initially captured and marked.
$n_{2}$	Total caught on the second occasion.
$n_{3}$	Marked individuals in the second capture.

Estimated N = 400

Follow the example steps

Divide by the number of marked individuals recaptured.

n₁ = 20, n₂ = 30, n₃ = 5: N = 20 × 30

N = 20 × 30/5 = 120

More checks before you submit

If no marked individuals are recaptured, the simple Lincoln estimate is undefined.

Method notes

The estimate depends on assumptions such as marks remaining identifiable, sufficient mixing, and similar capture probability.