Calculator Input Form
Enter population size, observed heterozygous individuals, and up to four allele frequencies. The calculator normalizes frequencies automatically when they do not total exactly one.
Example Data Table
These examples show how observed heterozygosity, expected heterozygosity, and FIS can vary across different biological samples.
| Sample | N | Het Count | A | B | C | D | Ho | He | uHe | FIS |
|---|---|---|---|---|---|---|---|---|---|---|
| River Frog Population | 120 | 46 | 0.55 | 0.30 | 0.15 | 0.00 | 0.3833 | 0.5850 | 0.5874 | 0.3447 |
| Forest Moss Survey | 90 | 33 | 0.40 | 0.35 | 0.20 | 0.05 | 0.3667 | 0.6750 | 0.6788 | 0.4568 |
| Seed Bank Collection | 150 | 88 | 0.25 | 0.25 | 0.30 | 0.20 | 0.5867 | 0.7450 | 0.7475 | 0.2125 |
Formula Used
This calculator estimates population-level diversity with observed and expected heterozygosity metrics. It also reports homozygosity, effective allele number, and an inbreeding coefficient estimate.
Observed heterozygosity (Ho) = Observed heterozygous individuals / Total individuals
Expected heterozygosity (He) = 1 - Σ(pi²)
Homozygosity = Σ(pi²)
Unbiased expected heterozygosity (uHe) = (2N / (2N - 1)) × He
Effective number of alleles = 1 / Σ(pi²)
Inbreeding coefficient (FIS) = 1 - (Ho / He)
Here, pi is the normalized frequency of each allele, and N is the total number of sampled individuals. If your frequencies do not sum to 1, the calculator rescales them before computing He.
How to Use This Calculator
- Enter a sample or population name for your records.
- Provide the total number of individuals sampled.
- Enter the number of observed heterozygous individuals.
- Fill in up to four allele frequencies for the locus you are studying.
- Select how many decimal places you want in the output.
- Click Calculate Heterozygosity to generate the results.
- Review Ho, He, uHe, homozygosity, effective alleles, and FIS.
- Use the CSV or PDF buttons to export the result section.
Frequently Asked Questions
1. What does heterozygosity measure?
Heterozygosity measures how often individuals carry two different alleles at one locus. Higher values usually suggest greater genetic diversity within the sampled population.
2. What is the difference between Ho and He?
Ho comes from the actual count of heterozygous individuals in your sample. He is the expected diversity calculated from allele frequencies under random mating assumptions.
3. Why does the calculator normalize allele frequencies?
Users often enter rounded frequencies that do not total exactly one. Normalization rescales them proportionally so expected heterozygosity can still be calculated correctly.
4. What does a high FIS value mean?
A positive FIS suggests fewer heterozygotes than expected, which can indicate inbreeding, substructure, or sampling effects. A negative FIS suggests excess heterozygotes.
5. Can I use more than four alleles?
This version supports four displayed allele inputs for simplicity. If your locus has more alleles, you can extend the form and calculation array with additional frequency fields.
6. Is this useful for conservation biology?
Yes. Heterozygosity is widely used to assess genetic diversity, compare populations, and monitor possible erosion of variation in endangered or managed groups.
7. What happens if He is zero?
If He is zero, all normalized allele weight is concentrated in one allele. In that case, FIS is not informative and is shown as unavailable.
8. Does this replace full population genetics software?
No. This tool is best for quick estimates, teaching, and reporting. Large multilocus studies still benefit from dedicated population genetics workflows and validation steps.