Calculate biodiversity index, total organisms, or species identified by entering any two values and solving the missing one with BI = S ÷ N.
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Biodiversity Index Formula
The calculator uses a simple biodiversity index based on the number of species identified divided by the total number of organisms counted.
BI = S / N
- BI = biodiversity index
- S = number of species identified
- N = total number of organisms counted
To calculate the missing value, the same formula can be rearranged:
S = BI * N
N = S / BI
- Calculate biodiversity index: enter total organisms and species identified. The calculator divides species identified by total organisms.
- Calculate species identified: enter total organisms and biodiversity index. The calculator multiplies the biodiversity index by total organisms.
- Calculate total organisms: enter species identified and biodiversity index. The calculator divides species identified by the biodiversity index.
Interpreting Biodiversity Index Values
This index ranges from 0 to 1 when the number of species identified is not greater than the total number of organisms. Higher values usually mean the sample has more species relative to the number of organisms counted.
| Biodiversity Index | General Meaning | Example Interpretation |
|---|---|---|
| 0 | No species recorded | No organisms or no species were identified in the sample. |
| 0.01 to 0.10 | Low species variety | Many organisms belong to a small number of species. |
| 0.11 to 0.50 | Moderate species variety | The sample contains several species compared with its total count. |
| 0.51 to 1.00 | High species variety | A large share of the organisms represent different species. |
Sample Count Checks
| Total Organisms | Species Identified | Biodiversity Index |
|---|---|---|
| 100 | 10 | 0.100000 |
| 80 | 20 | 0.250000 |
| 50 | 25 | 0.500000 |
Example Problems
Example 1: You count 120 total organisms and identify 18 species.
BI = 18 / 120 = 0.150000
The biodiversity index is 0.150000.
Example 2: You know the biodiversity index is 0.25 and the total number of organisms is 64.
S = 0.25 * 64 = 16
The number of species identified is 16.
FAQ
What does a higher biodiversity index mean?
A higher value means there are more identified species relative to the total number of organisms in the sample. For this calculator, a value closer to 1 means the sample has a high number of different species compared with its total count.
Can the number of species be greater than the total number of organisms?
No. Each species must be represented by at least one organism in the count. If you counted 40 total organisms, the number of species identified cannot be more than 40.
Is this the same as the Shannon or Simpson biodiversity index?
No. This calculator uses a simple ratio of species identified to total organisms. Shannon and Simpson indexes use the abundance of each species, so they require a more detailed breakdown of how many organisms belong to each species.
