Shannon Diversity Index Calculator

Ecological Biodiversity & Information Entropy

The Shannon Diversity Index (H) (also known as the Shannon-Wiener or Shannon-Weaver Index) originated in Claude Shannon's 1948 information theory to measure information entropy and was adapted by Robert MacArthur to quantify ecological biodiversity.

Primary Ecological Formulas

• Relative Abundance: p_i = (n_i) / (N)

• Shannon-Wiener Index: H = -Σ_i=1^S p_i (p_i)

• Maximum Possible Diversity: H_ = (S)

• Pielou's Evenness: E_H = (H) / (H_) = (H) / ((S)) (0 E_H 1)

• Effective Species: D = (H) = e^H

Typical Shannon Index Benchmark Values in Nature

• H < 1.5: Low diversity (disturbed habitats, agricultural monocultures, heavy pollution).

• 1.5 H 3.5: Moderate to healthy natural biodiversity (temperate deciduous forests, grasslands).

• H > 3.5: Exceptional biodiversity (tropical rainforests, undisturbed coral reef ecosystems).

How to Use This Calculator

Enter your Species Abundance Counts (Comma-Separated) (e.g. 50, 30, 20, 10, 5), Logarithmic Base — choose from Natural Logarithm (ln / base e — Ecological Standard), Base 2 (log₂ / bits — Information Theory), Base 10 (log₁₀ / decits), and Decimal Precision — choose from 2 Decimal Places, 4 Decimal Places, 6 Decimal Places. Results update instantly as you type — adjust any value to compare scenarios.

The Formula

Formula Reference: Shannon Diversity Index Calculator

Input variables:

speciesCountsList — Species Abundance Counts (Comma-Separated)

logarithmBaseSelect — Logarithmic Base

decimalPrecision — Decimal Precision

Computed outputs:

shannonDiversityIndexH — Shannon-Wiener Diversity Index (H)

pielouEvennessEH — Pielou's Species Evenness (E_H)

effectiveSpeciesCount — True Diversity / Effective Species (eᴴ)

speciesRichnessS — Species Richness (S)

totalSampleIndividualsN — Total Individuals Sampled (N)

Mathematical relationships extracted from calculation logic:

N = counts.reduce((acc, c) => acc + c, 0)

Standard: NIST / ISO mathematical definitions

Worked Example

Sampling 115 trees across 5 species (50 oaks, 30 maples, 20 pines, 10 birches, 5 ashes) yields an H of 1.3656 and evenness of 0.8485, confirming a balanced forest community equivalent to 3.92 equally common species.

Understanding Your Result

Evaluate your result in the context of your specific use case and relevant industry standards or reference values. A single calculated result is a starting point — test two to three scenarios to understand how sensitive the outcome is to your key input assumptions. For high-stakes decisions, verify your result against a secondary source or subject-matter expert before acting.