Simpson’s Diversity Index Calculator
🌍 Ecology. Use the Simpson’s diversity index (3 species) formula to find diversity d, species a count, species b count, species c count: pick the value you want, type the others, and the answer updates as you go.
From 0 (one species dominates) towards 1 (many species, evenly spread).
Pick the ○ next to the value you want to find, fill in the others, and it solves as you type.
What each letter means
| Quantity | Unit |
|---|---|
| Diversity D | no unit |
| Species A count | no unit |
| Species B count | no unit |
| Species C count | no unit |
Worked example
Find the diversity d when Species A count = 10, Species B count = 7, Species C count = 4.
Using D = 1 - (Σ n(n-1))/(N(N-1)): Diversity D = 0.65714.
Frequently asked questions
What is the formula for Simpson’s diversity index (3 species)?
D = 1 - (Σ n(n-1))/(N(N-1)). From 0 (one species dominates) towards 1 (many species, evenly spread).
What do the letters stand for, and what units are used?
Diversity D, Species A count, Species B count, Species C count.
How do you calculate diversity d?
Put the values into D = 1 - (Σ n(n-1))/(N(N-1)). For example, with Species A count = 10, Species B count = 7, Species C count = 4, diversity d = 0.65714.
Can I solve for a different value?
Yes. In the calculator above, pick the circle next to any value (diversity d, species a count, species b count, species c count) and fill in the others: it rearranges the formula for you.
