Statistics & Probability

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Simpsons Diversity Index Calculator.

Calculate this statistic instantly with validated formulas.

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Set your values

Results update as you type.

Result: Simpson concentration: 0.30000000 Simpson diversity (1 − D): 0.70000000 Total observations: 100

Result

Simpson concentration: 0.30000000 Simpson diversity (1 − D): 0.70000000 Total observations: 100

Use Cases

Ecological biodiversity assessment

Quickly compute Simpson's index for species abundance data from field surveys to compare biodiversity across habitats or time periods.

Example: Enter counts like 10, 20, 30, 40 to see how uneven distribution affects diversity.

Educational statistics practice

Use real or hypothetical category counts to understand how Simpson's index works and how it responds to changes in richness and evenness.

Example: Try 5,5,5,5 vs 1,1,1,97 to see the difference in diversity.

Frequently Asked Questions

What is Simpson's Diversity Index?
Simpson's Diversity Index measures the probability that two individuals randomly selected from a sample belong to the same species (concentration) or different species (diversity). It accounts for both species richness and evenness.
How do I use this calculator?
Enter the counts for each category (e.g., species abundance) in the 'Values' field, separated by commas or spaces. The calculator computes Simpson's concentration (D) and diversity (1-D) from your data.
What do the results mean?
Simpson's concentration (D) ranges from 0 to 1; higher values indicate dominance by one category. Simpson's diversity (1-D) is the complement; higher values indicate greater diversity. Both are based on your input counts.

Tips & Common Mistakes

Tips

  • Ensure all counts are non-negative numbers; zero counts are allowed but may affect the index.
  • Separate values with commas or spaces; avoid mixing separators in one input.
  • Use raw counts (not percentages) for accurate calculation.
  • Compare results across samples with the same total number of individuals for meaningful comparisons.

Common Mistakes to Avoid

  • Entering percentages or proportions instead of raw counts, which can skew the index.
  • Using commas and spaces together (e.g., '1, 2, 3') – stick to one separator.
  • Including negative numbers or text, which the calculator may not process correctly.

Last updated: August 13, 2026