Shannon Diversity Index Calculator — H' and Pielou's Evenness
Measure ecological diversity: enter the population count for each species and get the Shannon index H', the maximum possible diversity H_max, and Pielou's evenness J'.
Higher values indicate greater diversity; 0 = single species, H_max = perfect evenness
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Total count (N)
40 + 30 + 20 + 10 = 100 - 2
Shannon diversity index H'
−(0.4×ln(0.4) + 0.3×ln(0.3) + 0.2×ln(0.2) + 0.1×ln(0.1)) = 1.2799Each term pᵢ × ln(pᵢ) uses the relative abundance; the sum is negated.
How does this calculator work?
The Shannon index H' = −Σ pᵢ ln(pᵢ) measures ecological diversity using each species' proportion pᵢ of total individuals. Higher H' means more diversity; divide by H_max = ln(S) to get Pielou's evenness J' on a 0–1 scale. Typical ecological values range from 1.5 to 3.5.
Formula
How this is calculated
The Shannon diversity index H' borrows from information theory: it treats each species' relative abundance as the probability that a randomly chosen individual belongs to that species, then sums the self-information −pᵢ ln(pᵢ) over all species. A community with one dominant species has low H'; one where every species is equally abundant has the maximum possible value H_max = ln(S), where S is the number of species (richness).
Pielou's evenness J' = H' / H_max rescales the index to a 0–1 scale: 1 means perfectly equal abundances across all species, 0 would mean a single species holds everything. This separates the contribution of species richness from the effect of evenness, both of which drive H' upward.
This calculator uses the natural logarithm (base e) convention, which is most common in ecology. Some fields use log₂ (bits) or log₁₀; those values equal H_nats × log₂e ≈ H × 1.4427 and H × 0.4343 respectively. The index assumes observed counts are proportional to true abundances and that sampling is reasonably complete — heavily under-sampled communities will underestimate the true diversity.
Frequently asked questions
Typical values in ecology range from about 1.5 (low diversity) to 3.5 (high diversity), though the meaningful range depends on species richness. H' = 0 means only one species is present; H' = H_max = ln(S) means perfectly equal abundances. Context and comparison within the same habitat type matter far more than any single threshold.
Species richness simply counts how many species are present. The Shannon index also weights by relative abundance — a community with 10 equally common species scores higher than one where 9 rare species coexist with a single dominant species, even if richness is the same. Pielou's evenness isolates that weighting effect.
Yes — it is identical to the Shannon entropy used in information theory, and works for any categorical frequency data: word frequencies in a text, customer-segment distributions, genetic allele frequencies, network traffic by protocol. The interpretation is always 'how spread out is this probability distribution?'
TG we-Calculate Editorial Team. (2026). Shannon Diversity Index Calculator — H' and Pielou's Evenness [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/shannon-index-calculator
TG we-Calculate Editorial Team. "Shannon Diversity Index Calculator — H' and Pielou's Evenness." TG we-Calculate. 2026. https://we-calculate.com/calculator/shannon-index-calculator.
TG we-Calculate Editorial Team, "Shannon Diversity Index Calculator — H' and Pielou's Evenness," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/shannon-index-calculator
@misc{wecalculate_shannon_index_calculator, title = {Shannon Diversity Index Calculator — H' and Pielou's Evenness}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/shannon-index-calculator}}, year = {2026}, note = {TG we-Calculate} }
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