Tool · free
Biodiversity indices calculator
Paste a list of taxa and their abundances from a sample - one entry per line, e.g. Baetidae 12. The calculator computes the Shannon-Wiener index (H'), the Simpson index and Pielou evenness (J).
Paste at least two taxa with abundances.
How we calculate
For N individuals across S taxa, where pi is the share of the i-th taxon (ni/N):
Shannon-Wiener: H' = −Σ pᵢ × ln(pᵢ)
Pielou (evenness): J = H' / ln(S)
Simpson (dominance): D = Σ pᵢ² - the higher, the greater the dominance of single taxa
Simpson (diversity): 1 − D - the closer to 1, the greater the diversity
Frequently asked questions
In what format do I paste the data?
One entry (taxon) per line, name and abundance separated by a space, tab or comma - e.g. "Baetidae 12" or "Baetidae, 12". Order does not matter, and empty lines are ignored.
How does Shannon differ from Simpson?
The Shannon index (H') is sensitive to the number of taxa and their evenness - it rises when a sample has more groups of similar abundance. The Simpson index puts more weight on dominance - it reacts strongly when one taxon clearly prevails, even if the rest is diverse.
What does the Pielou index (J) show?
Evenness - the ratio of the measured H' to the maximum possible H' for that number of taxa (i.e. ln(S)). J close to 1 means taxon abundances are similar; J close to 0 means strong dominance by one or a few taxa.
How does it relate to BMWP-PL?
BMWP-PL speaks about water quality based on the PRESENCE of families sensitive to pollution. Diversity indices speak about the STRUCTURE and condition of the community - whether it is dominated by a few taxa or diverse. The same data (a list of taxa and abundances) can be computed with both tools - they give different, complementary information.
Sample composition from season to season
The value of diversity indices shows only in comparison - the same site, successive seasons. In LimnoLog you record taxon abundances as your own indicators and see how the community structure changes over time.
Open the app → Explore LimnoLog features →Read more