Run a soft tape measure around the base of your cat's neck, keep it snug but not tight, then add enough room to slide two fingers underneath flat. Most adult cats land between 20 and 30 cm, and almost every cat collar sold is adjustable across that range. The measurement matters less than the two-finger check, which you should repeat monthly.
Where the tape goes
Sit the tape at the base of the neck, where the collar will naturally rest, rather than high up near the jaw. Cats have more fur than neck, so press gently until you can feel where the neck actually is. If you do not own a soft tape, a strip of string or a phone charging cable works: wrap it, mark it with your thumb, then hold it against a ruler.
The two-finger rule
This is the part that matters. With the collar on, you should be able to slide two fingers flat between the collar and your cat's neck without forcing them. One finger means it is too tight. Four means your cat will have a front leg through it by lunchtime, which is one of the genuine hazards of a loose collar.
Why you re-check monthly
- Cats change weight. A winter coat, a summer moult, or a few gained pounds all move the fit.
- Fabric settles. Cotton and nylon both give a little in the first few weeks of wear.
- Young cats grow fast. A cat under a year old can outgrow a setting in weeks.
What about kittens?
We do not recommend collaring a cat under six months. They grow quickly enough that a correct fit goes wrong between checks, and they are the least equipped to deal with a collar that catches on something. Wait.
Long-haired cats
Measure against the neck, not the coat, or you will end up a full size out. It is also worth checking the fur under the collar every few weeks, since a collar sitting in one place on a long-haired cat can encourage a mat underneath. Sliding it around the neck a little when you do the fit check is usually enough.
The thing that matters more than fit
A perfectly measured collar without a breakaway catch is still a hazard. The catch is what opens if your cat snags the collar on a branch, a fence, or a latch, and it is the single most important feature on a cat collar. If yours does not release under a firm pull, replace it, whoever made it. We have written up why at length.
Our version
The Sakura Collar Set is soft plaid cotton with a breakaway catch and an adjustable strap that fits most adult cats. If you want your cat carrying an Apple AirTag, the Omamori Collar holds one in a silicone pocket, though it is worth reading what an AirTag can and cannot do first. Both live in Wear.