Inbreeding Coefficient Calculator
Estimate the COI of a planned mating and see whether it falls in a healthy range.
This free inbreeding coefficient (COI) calculator estimates the COI of offspring from a planned mating. In Quick mode, pick a relationship preset (for example first cousins at 6.25%, half siblings at 12.5%, or parent × offspring at 25%) and the tool shows that fixed percentage. In Advanced mode, list each ancestor that appears on both the sire and dam side; for each one you enter how many generations back it sits on each side (parent = 1, grandparent = 2, and so on).
The advanced total sums contributions of 0.5^(sireGen + damGen + 1) × 100 across every common ancestor you add, then displays the combined percentage. A colour band classifies the result as low (under 5%), moderate (5–10%), high (10–25%), or very high (25% and above) for quick comparison. This is a planning estimate only: a full pedigree COI from recorded ancestors can include more paths than you enter here.
Estimated offspring COI
12.50%
High inbreeding
This is an estimate for education. A precise COI requires a full multi-generation pedigree and Wright’s coefficient across all shared ancestors, which AllBreeds computes automatically from your animals’ recorded pedigrees.
What is a healthy COI?
- • Under 5% — low, comparable to breeding unrelated animals.
- • 5–10% — moderate line-breeding; commonly acceptable.
- • 10–25% — high; proceed only with strong justification.
- • Over 25% — very high; strongly discouraged.
Learn more in our guide on understanding the inbreeding coefficient.
COI calculator FAQ
How does this COI calculator estimate inbreeding?
In Quick mode it applies a fixed inbreeding percentage for common relationship presets (unrelated 0%, first cousins 6.25%, half siblings 12.5%, grandparent × grandchild 12.5%, full siblings 25%, parent × offspring 25%). In Advanced mode it adds 0.5 raised to (sire generations + dam generations + 1), times 100, for each ancestor you list on both sides, then sums those terms for the displayed offspring COI.
When should I use relationship presets versus advanced ancestors?
Presets are fastest when the mating matches a standard relationship label. Advanced mode is for multiple shared ancestors or non-standard paths: enter generation distance on the sire line and dam line for each common ancestor (1–10 generations). You can add or remove ancestor rows; the total updates from the sum of all rows.
What do the low, moderate, high, and very high bands mean?
The tool labels results under 5% as low, 5% up to but not including 10% as moderate, 10% up to but not including 25% as high, and 25% or more as very high. These bands mirror the reference ranges shown on the page; they are labels on the calculated percentage, not separate formulas.
Is this the same as a full pedigree COI calculation?
No. This page sums only the ancestors you enter (or a single preset). A complete coefficient from a multi-generation pedigree includes every shared ancestor and path. AllBreeds can compute COI from animals you store in the app when you use recorded pedigrees there.
Get exact COI from real pedigrees
AllBreeds calculates true multi-generation COI automatically from your animals’ recorded pedigrees.
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