# Shannon Diversity Index (H′ = −Σpᵢ·ln pᵢ) Compute Shannon H′ from species counts with H′max and Pielou evenness, in ln, log₂, or log₁₀ base. > Canonical page: https://elysiatools.com/en/tools/shannon-diversity-index - **Category:** Health - **Keywords:** shannon diversity index, shannon wiener, shannon weaver, species diversity, pielou evenness, richness, ecology calculator, biodiversity, community structure, entropy, evenness, lab calculator ## Overview Compute Shannon diversity H′ from species abundance counts, along with richness S, total N, H′max, and Pielou evenness J. Choose ln, log₂, or log₁₀ as the logarithm base. ## Inputs - **Species counts (one per line)** (textarea): One abundance count per species, separated by new lines, commas, or spaces. - **Logarithm base** (select) ## When to use - You have species abundance counts and need Shannon H′, H′max, and Pielou evenness J. - You want to compare evenness among samples that have similar species richness. - You need H′ in nats (ln), bits (log₂), or log₁₀ for a report or lab write-up. ## How it works - Enter one abundance count per species. Values can sit on separate lines or be separated by commas or spaces. - Choose the logarithm base: ln (classic ecology), log₂ (bits per species), or log₁₀. - The tool converts counts to proportions pᵢ = nᵢ/N, then computes H′ = −Σ pᵢ log pᵢ, H′max = log(S), and Pielou J = H′/H′max. - Results include S, N, proportions, H′, H′max, evenness J, the chosen base, and a short evenness interpretation. ## Use cases - Summarize plant or animal community structure from quadrat or transect counts. - Show how richness versus evenness changes Shannon H′ in teaching labs. - Report Shannon entropy and Pielou J from survey or lab abundance tables. ## Frequently asked questions ### What should I enter as species counts? One abundance per species. Separate values with new lines, commas, or spaces. Species names are not required. ### What does the calculator return? Richness S, total N, proportions, Shannon H′, H′max, Pielou evenness J, the log base, and a brief evenness interpretation. ### What is Pielou evenness J? J = H′ / H′max, where H′max is log(S). J runs from 0 to 1; J = 1 means all species are equally abundant. ### Which logarithm base should I use? Use ln for standard Shannon–Wiener reporting. Use log₂ for bits per species. Use log₁₀ when that unit is required. ### How should I read H′? H′ increases with both richness and evenness. Low S caps H′ even when evenness is high, so compare communities with similar S. ## Related tools - [A-a Gradient (Alveolar-Arterial O₂)](https://elysiatools.com/en/tools/a-a-gradient-calculator): Calculate the alveolar-arterial O₂ gradient to distinguish hypoxemia causes. PAO₂ = FiO₂×(P_atm−47) − PaCO₂/0.8; A-a = PAO₂ − PaO₂. Normal ≈ (Age+10)/4. Elevated → V/Q mismatch, shunt, diffusion impairment. Derived from StatPearls, LITFL, Cornell PICU, and Martin 1999. 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