Ecology & populations · SL/HL

Simpson reciprocal index

Calculate diversity from species counts.

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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D=\frac{N(N-1)}{\sum_i n_i(n_i-1)}

What the variables mean

Symbol	Meaning
$N$	Total number of individuals.
$n$	Number of individuals in each species.

Simpson reciprocal index = 4.313043

Follow the example steps

A larger reciprocal index indicates greater diversity under this convention.

For 5, 5 versus 9, 1: the lower index means greater diversity.

Counts 5, 5 give D = 2.25; counts 9, 1 give D = 1.25.

More checks before you submit

Do not enter species labels in the numerical list.
A larger reciprocal-index value indicates greater diversity under this convention.

Method notes

The index combines richness and evenness. Compare values only when sampling effort and method are comparable.