Coefficient of inbreeding: understanding a COI figure

Know what produced the number

The Royal Kennel Club’s calculator material explains its pedigree-based COI resource. When recording a figure, retain the calculator or laboratory, date and available pedigree or method context. Two percentages from different methods or ancestry coverage should not be treated as directly interchangeable merely because both are labelled COI.

A comparison example

Imagine one report using a shallow documented pedigree and another using a much larger ancestry dataset. A lower displayed figure does not automatically establish a less-related lineage when the underlying coverage differs. Ask the provider to explain the basis before using the numbers in an article, sales comparison or breeding discussion.

Keep interpretation appropriately qualified

COI is one piece of population and pedigree information, not a complete assessment of health, temperament or working ability. This page does not set a safe mating threshold or recommend a pairing. A consequential breeding decision needs appropriate professional advice and the wider evidence. If the source is incomplete, publish the limitation alongside the figure rather than presenting a precise number as certainty.

Sources & further reading

References for this guide. Rules and services can change; check the responsible organisation for current details.

• Royal Kennel Club — inbreeding calculators (opens in a new tab)

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