Inbreeding Coefficient Calculator
Calculate the inbreeding coefficient F from population size or known pedigree relationship. Determine probability of identity by descent and expected homozygosity increase.
🧬 Genetics📐 F = 1 - (1 - 1/2Ne)^t🧬 Biology
Effective population size Ne
Generations of inbreeding t
OR known relationship
Please enter valid values.
Formula & Reference
| Variable | Symbol | Formula | Units |
|---|---|---|---|
| Inbreeding Coefficient Calculator | — | F = 1 - (1 - 1/2Ne)^t | probability |
Step-by-Step Examples
Example 1
First Cousin Marriage
F for offspring of first cousins.
- First cousins share 1/8 of genes
- F = (1/2)^5 = 0.03125 = 3.125%
- Risk of recessive disease increases ~2-3x
✓ F = 0.0625 for first cousin offspring
Example 2
Small Population Ne=50
t=10 generations.
- F = 1-(1-1/100)^10 = 0.096
- 9.6% inbreeding in 10 generations
- Significant genetic erosion
✓ F = 0.096 after 10 gen (Ne=50)
Example 3
Zoo Population Ne=100
50 generations.
- F = 1-(1-0.005)^50 = 0.222
- 22% inbreeding
- Exceeds AZA 10% target in ~20 gen
✓ F = 0.222 after 50 gen
Real-World Applications
Conservation Management
Monitor F in captive breeding to prevent inbreeding depression.
Dog Breeding
Many breeds have high F linked to health problems.
Human Genetics
F elevation increases recessive disease prevalence in isolated populations.
Crop Breeding
Deliberate inbreeding creates homozygous lines for hybrid seed production.
Common Mistakes to Avoid
⚠️
F is probability, not certainty
F = probability that two alleles at a locus are identical by descent.
⚠️
F accumulates across generations
F_n = 1-(1-F_1)^n. Each generation adds F_1 of remaining heterozygosity.
⚠️
Full-sib gives highest F per generation
F = 0.25 per generation of full-sib mating, fastest route to homozygosity.
Frequently Asked Questions
What is identity by descent (IBD)? ▾
Two alleles are IBD if they are copies of the same ancestral allele. F = probability of IBD.
What is inbreeding depression? ▾
Reduced fitness due to expression of deleterious recessive alleles and loss of heterozygote advantage.
What F level causes inbreeding depression? ▾
Significant effects often start at F > 0.05-0.10. Highly variable by species.
How do zoos manage inbreeding? ▾
Species Survival Plans pair least-related animals, maximizing mean kinship and minimizing F.
What is genetic purging? ▾
Elimination of deleterious recessives through expression under inbreeding followed by selection.