The Breeder Collective

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Free tool · 01 Foundations & Planning

COI Calculator for Dogs

Enter the pedigrees of a sire and a dam to calculate the coefficient of inbreeding (COI) for a planned litter, or for a dog you already have. See which shared ancestors drive the number.

  • Wright’s coefficient, up to five generations
  • Shows each common ancestor’s share
  • Saved in your browser only

Step 1

Enter both pedigrees

Type each ancestor’s registered name or registration number, spelled exactly the same way every time it appears. That is how shared ancestors are found. Names you have typed are suggested as you go.

Your result

Enter the sire and the dam to begin

The COI updates as you type. Nothing is sent anywhere.

Reading the numberCOI is the probability that the two copies of a gene a puppy inherits are identical because they came from the same ancestor. A full-sibling or parent–offspring mating gives about 25%, and a half-sibling or grandparent–grandchild mating about 12.5%, if their own ancestors were unrelated. A pedigree COI only counts the generations you enter, so a deeper pedigree or a DNA-based COI is often higher. The Royal Kennel Club’s guidance is to aim at or below your breed’s average. Read more in Coefficient of inbreeding.
Coefficient of inbreedingWhat COI measures, and pedigree versus DNA-based COI.Read the article → Pedigree analysisHow to read a pedigree beyond the COI number.Read the article → Inbreeding and genetic diversityRelatedness, popular sires and your breed’s gene pool.Read the article →

This calculator uses Wright’s path method on the pedigree you enter. It assumes ancestors beyond those generations are unrelated, and it cannot tell two different dogs with the same name apart. It is general information to support your breeding decisions, not a health guarantee.