Species Diversity Index Calculator
Calculate Shannon-Wiener (H'), Simpson's Diversity Index, and evenness from species abundance data for up to 10 species.
About this calculator
Feed this calculator raw abundance counts for up to 10 species (any left at zero are automatically excluded, so you're not locked into exactly 10 species) and it computes the four diversity metrics most commonly reported in ecological surveys. Shannon-Wiener's H' (−Σ pᵢ ln pᵢ, using natural log) — introduced by Claude Shannon in his foundational 1948 paper on information theory and adopted by ecologists soon after as a diversity measure — rewards both the number of species present and how evenly individuals are distributed among them — it's sensitive to rare species, since even a single individual of an otherwise-unrepresented species nudges H' upward. Simpson's Diversity Index (1 − Σ pᵢ²), published by statistician Edward Simpson in a 1949 Nature paper, instead answers a more intuitive probability question: pick two individuals at random from the sample, what's the chance they're different species? It ranges from 0 to 1 and, unlike Shannon's H', is weighted toward the most common species rather than rare ones. The Simpson's Reciprocal (1/Σ pᵢ²) rephrases the same underlying sum as an "effective number of equally-common species," which is often easier to communicate to a non-specialist audience than either raw index.
Pielou's Evenness (J = H'/ln(S)), defined by E.C. Pielou in a 1966 paper on measuring diversity in biological collections, then normalizes Shannon's H' against the maximum possible diversity for the observed species richness, isolating how evenly individuals are spread from how many species there are — a value near 1 means every species is nearly equally abundant, while a low value flags a community dominated by one or two species even if total richness looks respectable. Berger-Parker Dominance (the single most abundant species' share of the total) is the simplest and most literal of the bunch, sensitive only to the single commonest species. Because Shannon's H' uses natural log here (not log₂ or log₁₀, both of which appear in some textbooks), don't cross-compare raw H' values against sources using a different log base — the relative comparisons within this calculator stay valid, but absolute numbers won't match a log₂-based Shannon index from elsewhere.
Inputs
Results
Shannon Index (H')
1.79
Simpson's Diversity (1-D)
0.8
Figures current as of 1966. Sources: Shannon, C.E. A mathematical theory of communication. The Bell System Technical Journal. 1948;27(3):379-423., Simpson, E.H. Measurement of diversity. Nature. 1949;163(4148):688., Pielou, E.C. The measurement of diversity in different types of biological collections. Journal of Theoretical Biology. 1966;13:131-144.
How to Use This Calculator
- Enter the individual count for each species (up to 10) from your quadrat or transect survey.
- Review Shannon Index (H') — higher values indicate greater diversity.
- Check Simpson's Diversity (1-D) for a probability-based complement to dominance.
- Note Pielou's Evenness (J) — values near 1 mean all species are equally abundant.
- Use these indices to compare diversity between sites, seasons, or treatment conditions.
How the result changes with Species 1 Count
| Species 1 Count | Shannon Index (H') | Simpson's Diversity (1-D) |
|---|---|---|
| 23 | 1.88 | 0.83 |
| 34 | 1.84 | 0.82 |
| 68 | 1.67 | 0.75 |
| 113 | 1.46 | 0.65 |
What each input means
- Species 1 Count
- Number of individuals observed for species 1.
- Species 2 Count
- Number of individuals observed for species 2.
- Species 3 Count
- Number of individuals observed for species 3.
- Species 4 Count
- Number of individuals observed for species 4.
- Species 5 Count
- Number of individuals observed for species 5.
- Species 6 Count
- Number of individuals observed for species 6. Set to 0 if unused.
- Species 7 Count
- Number of individuals observed for species 7. Set to 0 if unused.
- Species 8 Count
- Number of individuals observed for species 8. Set to 0 if unused.
- Species 9 Count
- Number of individuals observed for species 9. Set to 0 if unused.
- Species 10 Count
- Number of individuals observed for species 10. Set to 0 if unused.
What each result means
- Shannon Index (H')
- Higher values indicate greater diversity. Typical range: 0-4.
- Simpson's Diversity (1-D)
- Ranges 0-1. Higher = more diverse.
- Pielou's Evenness (J)
- 0 = uneven, 1 = perfectly even distribution among species.
- Berger-Parker Dominance
- Proportion of the most abundant species. Lower = more even.
How this is calculated
Figures and sources
- Shannon-Wiener diversity index (H' = -Σ pᵢ ln pᵢ) (1948) — Shannon, C.E. A mathematical theory of communication. The Bell System Technical Journal. 1948;27(3):379-423.
- Simpson's diversity index (D = 1 - Σ pᵢ²) (1949) — Simpson, E.H. Measurement of diversity. Nature. 1949;163(4148):688.
- Pielou's evenness index (J = H'/ln(S)) (1966) — Pielou, E.C. The measurement of diversity in different types of biological collections. Journal of Theoretical Biology. 1966;13:131-144.
Engine last updated . Checked against 1 independently-derived test — how we verify calculators. Built by Paul Gunder, a software engineer, not a licensed financial, medical, or legal professional.
Frequently Asked Questions
Why do Shannon's H' and Simpson's Diversity give different rankings for the same site sometimes?
Shannon's H' (−Σ pᵢ ln pᵢ) is more sensitive to rare species, since even one individual of an otherwise-unrepresented species nudges it upward, while Simpson's Diversity (1 − Σ pᵢ²) is weighted toward the most common species because squaring each proportion amplifies the dominant ones. A site with several rare species but one dominant species can score relatively higher on Shannon than on Simpson, since the two indices are answering different underlying questions about the community.
What does Simpson's Reciprocal (1/D) actually represent?
It rephrases the same Σ pᵢ² sum as an "effective number of equally-common species" — a value of 5 means the sample behaves, in terms of diversity, as if it contained 5 equally abundant species, even if the raw species count is higher. This is often easier to explain to a non-specialist than the 0-1 diversity index, since it maps onto an intuitive species-count scale.
Why does Pielou's Evenness matter if I already have Species Richness and Shannon's H'?
Evenness (J = H'/ln(S)) isolates how uniformly individuals are distributed among species from how many species are present in the first place — two sites can have identical species richness and very different evenness if one is dominated by a single species while the other has individuals spread roughly equally. A low evenness value flags dominance by one or two species even when the raw richness count looks healthy.
Can I directly compare this calculator's Shannon H' value against a value published in a paper?
Only if that paper also used natural log (base e) for its Shannon calculation — this calculator uses ln, not log₂ or log₁₀, both of which show up in some ecology textbooks and would produce a different numeric H' for the identical abundance data. Comparisons made entirely within this calculator (between sites, seasons, or treatments you enter here) stay valid regardless, since the log base is consistent across all of them.
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