What is the Shannon diversity index?

The Shannon diversity index (H'), also called the Shannon-Wiener index, measures biodiversity by combining species richness with the evenness of abundance distribution. A higher H' indicates greater diversity. It is calculated as H' = -Σ pᵢ × ln(pᵢ), where pᵢ is the proportion of individuals in species i.

What is a good Shannon diversity index value?

H' typically ranges from 0 (a community with only one species) to about 4-5 for very diverse communities. Values above 3 are generally considered high diversity. Tropical rainforests and coral reefs often exceed 3.5, while heavily disturbed habitats may fall below 1.

What is Pielou's evenness (J')?

Pielou's evenness J' = H' / ln(S) normalizes the Shannon index by the maximum possible diversity for S species. It ranges from 0 (one species dominates completely) to 1 (all species are equally abundant). J' tells you how evenly individuals are distributed among species.

Why does this tool use natural log (ln) instead of log base 2?

Both are valid. Using ln (nats) is the most common convention in ecology and gives H' in units of nats. Log base 2 gives bits, and log base 10 gives decibans. The choice of base does not change the relative ranking of communities.

What is the minimum number of species needed?

You need at least 2 species. With only 1 species, H' = 0 by definition (no diversity). This calculator requires at least 2 species with counts greater than zero.

Can I enter decimal counts (e.g., estimated densities)?

Yes. The formula works with any positive real numbers, not just integers. You can enter estimated densities, percentages, or biomass values as long as all entries are positive.

Shannon Diversity Index Calculator

Enter species names and abundance counts to instantly calculate Shannon diversity index H' and Pielou's evenness J'.

Species Abundance Data

Species Count

Quick Examples

Enter species and counts on the left, then click Calculate to see diversity results.

H' (Shannon)

—

nats

J' (Evenness)

—

0 – 1

Species (S)

—

richness

Total (N)

—

individuals

Evenness (J') —

0 — one species dominates 1 — perfectly even

Per-Species Breakdown

Species	n_i	p_i	ln(p_i)	p_i × ln(p_i)

Summary

The Shannon diversity index (H') quantifies biodiversity in a community by accounting for both species richness (number of species) and evenness (how equally individuals are distributed among species). It is calculated as H' = -Σ pᵢ × ln(pᵢ), where pᵢ is the proportion of individuals belonging to species i. Pielou's evenness (J') normalizes H' by the maximum possible diversity (ln S, where S is the number of species), giving a value between 0 and 1 that indicates how uniformly individuals are spread across species.

How it works

Enter each species name and its abundance count (number of individuals observed).
Click "Add Species" to add more rows, or remove any row with the minus button.
Click "Calculate" to compute H', species richness S, and Pielou's evenness J'.
Review the per-species breakdown table showing pᵢ, ln(pᵢ), and pᵢ×ln(pᵢ) for each species.
Use the quick-example presets to explore sample datasets from ecology.

Use cases

Ecology field surveys: compare biodiversity across different habitats or sampling sites.
Conservation biology: assess whether a restored ecosystem is approaching natural diversity levels.
Marine biology: measure species richness and evenness in reef or benthic communities.
Environmental impact assessment: quantify how pollution or land-use change affects diversity.
Microbiology and metagenomics: evaluate microbial community diversity from abundance data.
Student lab reports: compute H' and J' quickly and accurately for ecology coursework.
Longitudinal monitoring: track how diversity changes over seasons or years in a study area.

Frequently Asked Questions

Last updated: 2026-09-30 · Reviewed by Nham Vu