Species Evenness Calculator (Pielou's J)

Species Evenness Calculator

Evenness measures how equally individuals are distributed among species in a community, independent of how many species are present. Two habitats can have identical species richness but wildly different evenness - and very different ecological health as a result.

J = Shannon Index (H) / ln(Species Richness)

Example

Species counts of 40, 30, 20, 10 individuals:

Shannon Index H ≈ 1.28, ln(4 species) ≈ 1.39 → J = 1.28/1.39 = 0.92 (high evenness)

Reading the Score

J Value	Interpretation
> 0.75	High evenness - species relatively equally abundant
0.4 - 0.75	Moderate evenness - some species dominate
< 0.4	Low evenness - one or a few species strongly dominate

J ranges from 0 to 1, where 1 represents perfectly equal abundance across all species present. This measure is typically reported alongside species richness and diversity indices (like Shannon or Simpson's) to give a fuller picture of community structure than any single metric alone.