The Biodiversity Index Calculator is a free ecological analysis tool for calculating commonly used diversity measures from species abundance data. You can enter species counts manually or upload a CSV file to calculate Shannon diversity, Simpson diversity, species richness, Pielou evenness, Hill numbers, Margalef richness and Menhinick richness for one or several ecological communities.

The calculator is useful for ecological surveys, field studies, student projects and preliminary analysis of species abundance data. It can also compare diversity across multiple sites and generate downloadable results. If you are new to ecological communities, you may first want to read our guides to ecosystems, flora and fauna, and biological associations.

Calculate Biodiversity Indices

Use a single site name for one community, or enter several site names to compare ecological communities.

Input format: Enter a site/community, species or taxon name, and abundance. CSV files can contain site,species,count or simply species,count. Duplicate species within the same site are automatically combined.

Site / community	Species / taxon	Abundance	Remove

Analysis Results

Site Comparison

Site	N	S	Shannon H′	Hill q1	Simpson λ	Gini-Simpson	Hill q2	Pielou J′	Margalef	Menhinick

Interpretation note: There is no universal numerical cutoff that makes a Shannon, Simpson or richness value “low”, “moderate” or “high” for every ecosystem. Compare values only in the context of the habitat, sampling design, taxonomic resolution, sample size and study objective.

Visual Site Comparison

Metric:

Rank-Abundance View

Site:

Species are ranked from most to least abundant. Bar length represents relative abundance within the selected site.

Species-Level Calculations

Site	Species	n	pᵢ	−pᵢ ln(pᵢ)	pᵢ²	nᵢ(nᵢ−1)

Export Results

Formulas Used by the Calculator

Shannon diversity: H′ = −Σ pᵢ ln(pᵢ), where pᵢ = nᵢ/N.

Hill number q1: exp(H′). This expresses Shannon diversity as the effective number of equally common species.

Simpson concentration: λ = Σ pᵢ². Larger values indicate greater concentration or dominance.

Gini-Simpson diversity: 1 − λ. Larger values indicate greater diversity.

Hill number q2 / reciprocal Simpson concentration: 1/λ.

Finite-sample Simpson estimate: λ̂ = Σ nᵢ(nᵢ−1) / [N(N−1)]. It is displayed separately because several Simpson conventions are used in ecological literature.

Pielou evenness: J′ = H′ / ln(S).

Margalef richness: (S−1) / ln(N).

Menhinick richness: S / √N.

Method note: Species with zero abundance are excluded. Duplicate species names within a site are merged case-insensitively before calculation. If only one species is present, Pielou evenness is not defined. If N = 1, the finite-sample Simpson estimate is not defined.

What Is a Biodiversity Index?

A biodiversity index is a quantitative measure used to describe the variety and distribution of organisms in an ecological community. Different indices measure different components of diversity. Species richness records how many species are present, whereas Shannon and Simpson measures also consider how individuals are distributed among those species.

For this reason, biodiversity is often better described using several complementary measures rather than a single index. Two ecosystems can contain the same number of species but have very different community structures if one is dominated by only one or two species while the other has a more even distribution of abundance.

Biodiversity patterns also vary among forests, grasslands, wetlands, deserts and aquatic environments. See our overview of the major types of ecosystems for additional ecological context.

How to Use the Biodiversity Index Calculator

Enter the name of the site or ecological community.
Enter each species or taxon and its observed abundance.
For a single community, use the same site name for all species.
To compare communities, assign the corresponding site name to each species record.
Click Calculate biodiversity indices.
Review the calculated indices, site comparison and rank-abundance display.
Download the calculated results or cleaned abundance data if required.

You can also import data directly from a CSV file. The preferred structure is:

site,species,count
Forest A,Species A,32
Forest A,Species B,18
Forest A,Species C,9
Forest B,Species A,15
Forest B,Species B,24
Forest B,Species C,17

For a single community, a two-column file containing species,count can also be used.

Biodiversity Indices Calculated by This Tool

Measure	What it describes	General interpretation
Species richness (S)	Number of species or taxa represented by positive abundance records.	More observed taxa produce a larger value, although sampling effort strongly influences richness.
Shannon diversity (H′)	Combines species richness and relative abundance.	Usually increases as richness and evenness increase.
Hill q1	Effective number of species derived from Shannon diversity.	Represents the number of equally common species that would produce the observed Shannon diversity.
Simpson concentration (λ)	Concentration of abundance among species.	Larger values indicate greater dominance.
Gini-Simpson diversity (1−λ)	Diversity transformation of Simpson concentration.	Larger values indicate greater diversity.
Hill q2	Effective number of species based on Simpson concentration.	Places greater weight on common species and less on rare species.
Pielou evenness (J′)	How evenly individuals are distributed among observed species.	Approaches 1 when species have similar abundances.
Margalef richness	Species richness scaled partly by total abundance.	Useful for descriptive comparisons when sampling methods are comparable.
Menhinick richness	Species richness scaled by the square root of total abundance.	Provides another richness measure that accounts for sample size.

Shannon Diversity Index

The Shannon diversity index, commonly written as H′, incorporates both the number of species and the relative abundance of each species. For species i, the relative abundance is calculated as p_i = n_i/N, where n_i is the abundance of that species and N is the total number of individuals in the sample.

H′ = −Σ p_i ln(p_i)

A community containing many species with relatively similar abundances generally has a higher Shannon value than a community with the same richness but strong dominance by one or two species. This calculator uses the natural logarithm.

Simpson Index and Gini-Simpson Diversity

The term Simpson index is used for several related measures in ecological literature and software. To avoid ambiguity, this calculator reports each formulation explicitly.

The proportion-based Simpson concentration is:

λ = Σ p_i²

A larger λ indicates that abundance is concentrated among fewer species. The corresponding Gini-Simpson diversity is:

1 − λ

In this form, larger values represent greater diversity. The calculator also reports 1/λ, which is the Hill number of order q = 2, and separately reports the commonly used finite-sample formulation:

λ̂ = Σ n_i(n_i−1) / [N(N−1)]

When reporting a Simpson measure in a thesis, research paper or ecological survey, it is good practice to state the exact formula rather than reporting only the term “Simpson index”.

Hill Numbers and Effective Number of Species

Hill numbers provide a unified way to express several common biodiversity measures as an effective number of species. This makes diversity values easier to interpret and compare.

q = 0: species richness S.
q = 1: exp(H′), corresponding to Shannon diversity.
q = 2: 1/λ, corresponding to reciprocal Simpson concentration.

For example, a Hill q1 value of 5 means that the observed Shannon diversity is equivalent to a hypothetical community containing five equally abundant species.

Pielou Evenness Index

The Pielou evenness index describes how evenly abundance is distributed among the species observed in a community:

J′ = H′ / ln(S)

Values approach 1 when the observed species have similar abundances. The index is not defined by this formulation when only one species is present because ln(1) equals zero.

Margalef and Menhinick Richness Indices

Observed species richness is affected by the number of individuals collected. Margalef and Menhinick indices provide simple approaches for scaling richness by total abundance.

Margalef richness = (S − 1) / ln(N)

Menhinick richness = S / √N

These indices are useful for descriptive analysis, but they do not completely remove the influence of unequal sampling effort. Rarefaction or coverage-based approaches may be preferable when sampling completeness differs substantially among sites.

Worked Biodiversity Calculation Example

Consider an ecological sample containing five species with abundances of 42, 27, 18, 11 and 8 individuals. The total abundance is 106 and species richness is 5. The Biodiversity Index Calculator gives approximately:

Shannon H′: 1.4464
Hill q1: 4.2477
Simpson concentration λ: 0.2672
Gini-Simpson diversity: 0.7328
Hill q2: 3.7428
Pielou evenness: 0.8987
Margalef richness: 0.8577
Menhinick richness: 0.4856

You can reproduce these results by selecting Single-site example in the calculator.

Shannon vs Simpson Diversity: Which Index Should You Use?

Shannon and Simpson measures respond differently to community composition. Shannon diversity is more sensitive to rare species, whereas Simpson-based measures place greater weight on common and dominant species.

Reporting both can therefore provide complementary information. Hill q1 and q2 are especially useful because they express these measures in the common unit of effective species.

How to Interpret Biodiversity Index Values

There is no scientifically universal Shannon, Simpson, Margalef or Menhinick threshold that divides all ecosystems into low, moderate and high biodiversity. A value measured in a tropical forest cannot automatically be interpreted using the same scale as a wetland, agricultural field, desert, freshwater community or microbial sample.

Interpretation should consider sampling effort, season, taxonomic resolution, habitat type, spatial scale, sampling completeness, species detectability and the ecological question being investigated.

This is especially important in highly diverse conservation areas. Our guide to biodiversity hotspots explains why species richness and conservation significance can vary greatly across regions.

Comparing Biodiversity Between Sites

The multi-site mode calculates alpha-diversity measures independently for each ecological community. It is suitable when you want to compare richness, evenness, Shannon diversity or Simpson-based diversity among sites sampled using comparable methods.

If the objective is to determine how species composition changes between communities, beta-diversity measures may be more appropriate. Jaccard similarity, Sørensen similarity and Bray-Curtis dissimilarity quantify different aspects of compositional similarity and turnover. Read our detailed guide to beta diversity for an explanation of these measures.

Why Sampling Effort Matters

Most biodiversity indices are influenced directly or indirectly by sampling. A larger sample may detect species that were missed in a smaller sample, increasing observed richness and potentially changing other diversity values.

When comparing sites, use comparable sampling methods, effort, season and taxonomic resolution wherever possible. If sampling intensity differs strongly among sites, rarefaction, extrapolation or coverage-based diversity analysis may be more appropriate than a simple comparison of observed richness.

Limitations of Biodiversity Indices

A biodiversity index summarizes ecological data but cannot replace a suitable study design or ecological interpretation. Index values may differ because of sampling effort, detectability, season, habitat size or taxonomic identification rather than a true change in biodiversity.

Diversity indices also do not indicate whether particular species are native, invasive, threatened or ecologically desirable. A disturbed site containing numerous invasive species could have relatively high numerical diversity while still having poor conservation value.

For advanced ecological studies, diversity indices may therefore need to be combined with species composition, functional diversity, phylogenetic diversity, environmental variables and appropriate statistical analysis.

Frequently Asked Questions

What data are needed to calculate biodiversity?

You need a list of species or taxa and the abundance of each taxon in a sample. For site comparisons, the same type of abundance measurement and comparable sampling methods should be used.

Can this calculator be used for plants, animals and microorganisms?

Yes. The mathematical indices can be applied to any ecological dataset consisting of categories or taxa with abundance data. Interpretation should reflect the organisms, taxonomic resolution and sampling method used.

Can I upload a CSV file?

Yes. The calculator accepts CSV data containing site, species and count fields. A two-column species-and-count format can also be used for a single community.

What happens if I enter the same species twice?

Duplicate species names within the same site are merged automatically without regard to capitalization, and their abundances are summed before diversity is calculated.

Does the calculator include species with zero abundance?

No. Zero-abundance records are excluded because a taxon that is absent from the observed sample does not contribute to observed richness or abundance-based diversity.

Is a higher Shannon index always ecologically better?

No. A higher Shannon value generally indicates greater richness and/or evenness, but it does not directly measure ecosystem health or conservation value. Species identity, habitat condition and ecological context also matter.

Why are several Simpson values shown?

The term Simpson index can refer to several related equations. The calculator therefore labels Simpson concentration λ, Gini-Simpson diversity 1−λ, Hill q2 = 1/λ and the finite-sample Simpson estimator separately.

Can Shannon values from different studies be compared directly?

Only with caution. Sampling method, taxonomic scope, sample size, season and detection probability can influence the values. Within-study comparisons using standardized methods are generally more defensible.

Related Ecology and Biodiversity Resources

Scientific References

Shannon, C.E. (1948). A mathematical theory of communication. Bell System Technical Journal, 27, 379–423 and 623–656.
Simpson, E.H. (1949). Measurement of diversity. Nature, 163, 688. doi:10.1038/163688a0.
Margalef, R. (1958). Information theory in ecology. General Systems, 3, 36–71.
Menhinick, E.F. (1964). A comparison of some species-individuals diversity indices applied to samples of field insects. Ecology, 45, 859–861. doi:10.2307/1934933.
Pielou, E.C. (1966). The measurement of diversity in different types of biological collections. Journal of Theoretical Biology, 13, 131–144. doi:10.1016/0022-5193(66)90013-0.
Hill, M.O. (1973). Diversity and evenness: A unifying notation and its consequences. Ecology, 54, 427–432. doi:10.2307/1934352.

Use of this tool: This calculator is intended for education, ecological data exploration and research support. Users should confirm that the selected diversity measure, sampling design and statistical interpretation are appropriate for their study.