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Biology Tools · Updated October 21, 2026 · Reviewed by FormatFlow Editorial

Shannon Diversity Index Calculator

You can calculate the Shannon diversity index H′ from species counts, with species richness, evenness, Simpson's index and a per-species contribution table shown in your browser.

Runs in your browserFree · No sign-up · No watermark
COUNTS → H′Runs in your browser
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Everything runs locally in this tab. No file is uploaded while the tool loads.

This tool runs in your tab. Nothing is uploaded and no copy is stored.

How files are handled

At a glance

Works with
COUNTS → H′
Processing
In your browser
Price
Free, no account
Updated
October 21, 2026
All Biology Tools

About Shannon Diversity Index Calculator

The Shannon diversity index, also called the Shannon–Wiener index, summarises how many species a community contains and how evenly individuals are spread across them. It is a standard measure in ecology and can be calculated by hand for small samples, which makes it a common practical question in coursework and fieldwork.

This calculator takes species counts one per line, or names with counts, and returns H′ = −Σ pᵢ ln pᵢ together with species richness, total individuals, evenness and optionally Simpson's index of diversity. A contribution table shows each species' share, so an unexpected value can be traced back to the input that caused it.

What this tool does

The details that matter when you use Shannon Diversity Index Calculator for real work.

  • Counts or named species

    Enter bare counts one per line or write Name, count; blank lines are ignored and names are carried into the results table.

  • Shannon index with working

    H′ = −Σ pᵢ ln pᵢ is shown with the computed value using natural logarithms, the usual convention for this index.

  • Richness and evenness

    Species richness S and evenness J′ = H′ / ln S are reported, with a clear note when a single species makes evenness undefined.

  • Per-species contribution

    The table lists pᵢ, ln pᵢ and −pᵢ ln pᵢ for every species, with a total that matches H′ so the arithmetic can be checked.

  • Optional Simpson's index

    A checkbox adds Simpson's index of diversity, D = 1 − Σ pᵢ², which weights common species more heavily than the Shannon index does.

  • Input validation

    Zero, negative, decimal and non-numeric counts are rejected with the line number that needs fixing.

How to use Shannon Diversity Index Calculator

No account, no installation — the whole job happens in this browser tab.
  1. 01

    Enter the counts

    Type one whole-number count per line, or write a species name, a comma and the count, for example Oak, 120.

  2. 02

    Add names if you like

    Names are optional; without them the table labels each row Species 1, Species 2 and so on in input order.

  3. 03

    Choose whether to show Simpson's index

    Leave the checkbox on for Simpson's D = 1 − Σ pᵢ², or turn it off when you only need the Shannon index.

  4. 04

    Read H′, richness and evenness

    The summary cards show the Shannon index, species richness, evenness and the total number of individuals.

  5. 05

    Check the contribution table

    Scan the −pᵢ ln pᵢ column to see which species contribute most, and confirm that the total matches the reported H′.

How this tool works

Works with
COUNTS → H′
Processing
Client-side, in your browser. Nothing is uploaded.
Requirements
Chrome, Edge, Firefox or Safari · JavaScript enabled

Limitations worth knowing

  • Requires whole-number counts; percentages, biomass and other non-integer abundances must be converted before they can be entered.
  • H′ and evenness depend on sample size and sampling effort, so values from differently collected surveys are not directly comparable.
  • A single index hides species identity and can miss rare species in small samples, so richness and the contribution table are shown alongside it.

Privacy and file handling

The counts you enter stay in this browser tab. Parsing and every index calculation run with JavaScript on your device, so nothing is uploaded, stored or logged, and closing the page discards the input and results.

Read the full privacy policy

Shannon Diversity Index Calculator FAQ

Short, direct answers to the questions people ask before using this tool.
How is the Shannon diversity index calculated?
For each species, divide its count by the total number of individuals to get pᵢ, multiply pᵢ by the natural logarithm of pᵢ, and add the negative of those values: H′ = −Σ pᵢ ln pᵢ. The index is 0 when one species dominates and rises with richness and evenness.
What is the difference between Shannon and Simpson diversity?
The Shannon index weights species roughly by their relative abundance and is sensitive to rare species. Simpson's index of diversity, 1 − Σ pᵢ², weights common species more heavily and therefore falls faster when one species dominates. Reporting both gives a fuller picture.
Why is evenness undefined when there is only one species?
Evenness is H′ divided by ln S, and with one species S = 1, so ln S is 0 and the division is undefined. The community also has H′ = 0, so the tool reports the index and richness but marks evenness as not applicable.
Can I use percentages or biomass instead of whole-number counts?
The calculator accepts whole numbers only, because that is how counts are recorded. Convert percentages or biomass to counts first, or scale relative abundances to a common total, and remember that the index describes proportions rather than absolute population size.
What does a good Shannon diversity value look like?
There is no universal threshold. H′ depends on both species richness and evenness, and it can exceed 3 in very diverse communities. Compare values from similar habitats and sampling methods, and read richness and evenness alongside the index.
Can I compare Shannon indexes from different surveys?
Only cautiously. Sampling effort, sample size and the area surveyed all affect H′, and rare species are easily missed in small samples. Compare samples collected in comparable ways, or use methods designed for rarefaction and statistical comparison.
Does the calculator report the effective number of species?
No, it reports H′ directly. If you need the effective number of species, exponentiate the index: e raised to the power of H′ gives Hill number 1, which is measured in species rather than in log units.
Are my counts uploaded anywhere?
No. Parsing, the index calculation and the contribution table all run with JavaScript in this browser tab, so the counts are never uploaded, stored or logged, and closing the page discards them.

Background reading

Format guides that explain the trade-offs behind Shannon Diversity Index Calculator.