Genetic Diversity / COI Calculator
The Coefficient of Inbreeding (COI) is the single most important number in ethical breeding decisions. It measures how genetically similar the sire and dam are — the higher the number, the greater the risk that hidden recessive diseases will express in the litter. This calculator gives a quick estimate based on shared ancestors and generations back, plus context on what each COI band means (0-6.25% ideal, 25%+ full-sibling level and dangerous). For final decisions, always run a full 10-generation pedigree COI through breed-club or veterinary software.
Full 5-generation pedigrees give the most reliable estimate.
Reference bands:
- 0-6.25% — unrelated to distant cousins (ideal)
- 6.25-12.5% — first-cousin equivalent
- 12.5-25% — half-sibling equivalent
- 25%+ — full-sibling / parent-offspring (avoid)
For accurate pedigree-based COI, use software like Breedmate or the breed database's COI calculator with a full 10-generation pedigree.
Examples
- 1 shared ancestor 5 generations backCOI ≈ 0.05% (Low)
- 3 shared ancestors 3 generations backCOI ≈ 2.3% (Low)
- Full-sibling pairingCOI ≈ 25% (Very High — do not breed)