Simpson's Diversity Index Calculator

Your details

Use "finite" for field counts where the sample is small relative to the population (the most common choice). Use "infinite/proportions" when working from estimated proportions of a very large population.
Number of individuals observed for species 1. Leave at 0 to omit.
Number of individuals observed for species 2. Leave at 0 to omit.
Number of individuals observed for species 3. Leave at 0 to omit.
Number of individuals observed for species 4. Leave at 0 to omit.
Number of individuals observed for species 5. Leave at 0 to omit.
Number of individuals observed for species 6. Leave at 0 to omit.
Number of individuals observed for species 7. Leave at 0 to omit.
Number of individuals observed for species 8. Leave at 0 to omit.
Number of individuals observed for species 9. Leave at 0 to omit.
Number of individuals observed for species 10. Leave at 0 to omit.
Gini-Simpson Index (1 - D)Moderate diversity
0.6241

Probability that two randomly chosen individuals belong to different species (0 = no diversity, 1 = maximum diversity).

Simpson's Index (D)0.3759
Reciprocal Index (1/D)2.66
Species Richness (S)3
Species Evenness0.8868
Total individuals (N)250
0.6241
Low diversity<0.3Moderate-low0.3-0.5Moderate0.5-0.7High0.7-0.85Very high0.85+
D (dominance)0.3759
1 - D (diversity)0.6241
Evenness0.8868

Gini-Simpson index is 0.6241 - moderate diversity.

  • Simpson's D is 0.3759, meaning there is a 37.6% chance that two randomly picked individuals belong to the same species.
  • The reciprocal index (1/D = 2.66) is equivalent to 2.66 effective species out of 3 observed - the effective number of equally-abundant species that would produce this diversity score.
  • Species evenness is 0.887 (very even): a score of 1.0 would mean all 3 species have identical counts.
  • Your sample contains 250 total individuals across 3 species.

Next stepCompare this result with the Shannon-Wiener index, which weights rare species more heavily and can give a different picture of community structure.

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