Shannon Diversity Index Calculator

The Shannon Diversity Index (H), also called the Shannon-Wiener or Shannon-Weaver index, is a metric used in ecology to measure species diversity within a community. It accounts for both the number of species present (richness) and how evenly individuals are distributed among those species (evenness). A higher H value indicates greater diversity.

The formula is H = −∑[pᵢ × ln(pᵢ)], where pᵢ is the proportion of individuals belonging to species i (i.e., nᵢ / N, the count of species i divided by the total count). The sum is taken over all species present, and the negative sign ensures the result is positive.

H reflects both species richness and evenness in a single number. A community with many species all at equal abundances will have a high H, while a community dominated by one species will have a low H. It helps ecologists compare the biodiversity of different habitats or track changes in a habitat over time.

Yes. When using natural logarithm (ln), H can range from 0 (only one species present) up to ln(S), where S is the number of species. In practice, most ecological communities have H values between 1.5 and 3.5, and values above 3 indicate very high diversity. The index is not capped at 1.

An H of 0 means only one species is present. Values between 0 and 1.5 suggest low diversity, 1.5–2.5 moderate diversity, and above 2.5 high diversity. For easier interpretation, use Shannon Evenness (E = H / H_max), which ranges from 0 to 1 — values near 1 mean species are very evenly distributed.

Shannon Evenness (E) is calculated as H / H_max, where H_max = ln(S) is the maximum possible diversity for S species. E ranges from 0 to 1. A value of 1 means all species are equally abundant (perfect evenness), while values closer to 0 indicate that a few species dominate the community.

Natural logarithm (ln, base e) is the most common choice in ecological literature and is the default in this calculator. Log base 2 is sometimes used in information theory contexts, while log base 10 is less common in ecology. The choice affects the numerical value of H but not the relative comparisons between communities — just be consistent within a study.

This calculator supports up to 10 species. A 'species' can be any taxonomic or categorical group you are comparing — actual biological species, morphospecies, genera, or any other unit of biodiversity relevant to your study. Simply leave unused species fields at 0 and they will be excluded from the calculation.