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Checking a pairing: COI & trial matings
Before two cats ever meet, you can see what their kittens’ pedigree would look like — and get a plain-English read on whether the pairing is too close. Here’s how.
What does COI actually mean?
COI stands for coefficient of inbreeding. It sounds technical, but the idea is simple: it’s a way of measuring how closely related two cats are by looking back through their family trees and counting the ancestors they share. The more ancestors a sire and dam have in common — and the closer up those shared ancestors sit — the higher the figure.
Put plainly, COI answers one question for you: is this pairing too close? A low figure means the two cats are only distantly related. A higher figure means they share a lot of the same family, which is something many breeders prefer to keep an eye on. Perfect Pedigrees does all the counting for you, so you don’t need to work anything out by hand.
Run a trial mating before the cats meet
A trial mating lets you test a pairing on paper first. You don’t commit to anything — you simply pick a possible sire and a possible dam, and we show you the pedigree their kittens would have, along with the COI for that combination. It’s the safest way to explore your options before any travelling, stud fees or arrangements are made.
- Open the trial-mating screen.
- Choose a sire from your own cats or the shared pool.
- Choose a dam the same way.
- We build the resulting pedigree on screen and show you the COI and diversity figure for the pairing.
Reading the result and the diversity figure
Alongside the COI, we show a diversity figure — think of it as the other side of the same coin. Where COI tells you how much family the two cats share, diversity gives you a feel for how varied the resulting kitten’s ancestry would be. A higher diversity figure generally points to a wider, more mixed family tree.
The two figures are best read together. A pairing with a low COI and a healthy diversity figure is, broadly speaking, a less closely related match. As you try different sires and dams, you’ll quickly see how the numbers move — and that makes it much easier to compare your options side by side.
What’s a sensible range?
There’s no single “right” number that fits every breed and every breeding plan, so we won’t pretend there is. What we will say is that lower COI figures mean a less closely related pairing, and many breeders use a trial mating to keep an eye on the trend rather than to chase one magic value. The figure that matters most is the one judged against your breed, your lines and your own goals.
The real value of running trial matings is that you can compare several pairings calmly, in your own time, before anything is decided. It turns a gut-feel decision into an informed one — and it’s completely free to do as often as you like. To see where this fits in the wider workflow, take a look at how it works, or read more about the certificates you can produce once you’ve settled on a pairing.
