Biology

Shannon and Simpson Diversity Index Calculator

Enter the number of individuals of each species to get diversity indices.

By TheCalcTools Updated October 17, 2026 Formula checked and tested

Your numbers

Individuals per species

Separate numbers with commas, spaces or new lines. You can paste a column from a spreadsheet.

Your results

Shannon index H′

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Pielou's evenness J′

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Simpson's index of diversity (1 − D)

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Inverse Simpson (1/D)

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Species richness

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Total individuals

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Shannon and Simpson Diversity Index Calculator by TheCalcTools

How the Shannon and Simpson Diversity Index Calculator works

The Shannon index H′ = −Σ pᵢ ln pᵢ rises with both the number of species and how evenly individuals are spread among them. Evenness J′ divides H′ by its maximum, ln S.

Simpson’s D is the chance that two individuals picked at random (without replacement) are the same species; 1 − D is the chance they differ.

The formula

H′ = −Σ pᵢ ln pᵢ; J′ = H′ ÷ ln S; D = Σ n(n − 1) ÷ (N(N − 1))

Worked example

Using the default values shown in the calculator:

Individuals per species	40, 25, 15, 10, 6, 4

Six species, 100 individuals: H′ = 1.525, evenness 0.851.
Simpson’s 1 − D = 0.747.

Result:

Shannon index H′	1.5255
Pielou's evenness J′	0.8514
Simpson's index of diversity (1 − D)	0.7473
Inverse Simpson (1/D)	3.957
Species richness	6
Total individuals	100

Frequently asked questions

Which index should I use?

Shannon weights rare species more; Simpson emphasises dominant species. Many studies report both.

Sources and further reading

Wikipedia: Diversity index