Ecology & populations · SL/HL
Simpson Reciprocal Diversity Index Calculator
Enter the number of individuals observed in each species, separated by spaces, commas or new lines.
Your values
Start with the example or enter your own values. Use a dot for decimals and e for scientific notation.
Calculated locally. No account or input upload.
Result & working
ExampleThe calculator is loading. The worked example is also shown below.
Step-by-step working
The formula
reciprocal index = N(N−1) / Σ[n(n−1)]
| Symbol | Meaning |
|---|---|
| N | Total number of individuals. |
| n | Number of individuals in each species. |
When to use this calculator
The index combines richness and evenness. Compare values only when sampling effort and method are comparable.
Worked example
The page opens with these example values. The result below is pre-generated for reference.
- N = Σn = 32
- Σn(n−1) = 12×11 + 8×7 + 5×4 + 5×4 + 2×1 = 230
- D = N(N−1)/Σn(n−1) = 32×31/230 = 4.313043
Simpson reciprocal index = 4.313043
Common mistakes
- Do not enter species labels in the numerical list.
- A larger reciprocal-index value indicates greater diversity under this convention.