The short answer for a Scottish Fold
Most adult Scottish Folds fit a medium carrier about 19 to 21 inches long, 12 to 13 inches wide, and 12 to 13 inches tall. The width matters more here than it does for a lean breed, because a Scottish Fold is a compact, round-bodied cat with a broad chest and a tendency to sit like a little owl, legs tucked and back upright. She should be able to stand with her folded ears clear of the roof, turn around without her shoulders scraping the walls, and lie on her side with her legs stretched. If she can only crouch or fold herself into a tight ball, the carrier is too small even if the length looks generous on paper.
Why width and headroom matter for a Fold
A Scottish Fold's folded ears change the way you judge headroom. The ears lie close to the skull, so the top of the head is the true high point, and a carrier roof that looks tall enough from outside may still press close when a thick pad is added inside. Measure your Fold standing on a flat surface, from the floor to the highest point of her head, and compare that figure with the carrier's interior height after the pad is in place. Her stocky build also means her weight can mislead you: a Fold of moderate weight may still need a wider carrier than a longer, lighter cat.
Door style and handling for a seated, social cat
Scottish Folds are famously social and often follow their people from room to room, which makes carrier training easier than with a shy breed, but it also means a Fold may try to climb out the moment a door opens. A carrier with a secure, latched front door plus a top opening gives you two calm options: you can set her in from above when she is relaxed, or guide her through the front while a second person steadies the carrier. Avoid carriers whose doors rely on a single flimsy clip, because a strong, determined Fold can nose at a weak latch.
Turning the carrier into a Scottish Fold's own spot
Because Scottish Folds enjoy being near their people, the carrier works best when it lives in a shared room rather than in a closet. Place it near a favourite chair or window perch, door open, with a thin pad and a familiar-smelling blanket inside. Many Folds will claim it as a nap spot within days, especially if treats appear just inside the entrance. That familiarity pays off at the vet, where a Fold who knows her carrier will often sit calmly instead of scrambling. A Fold who has already napped in her carrier at home usually rides with far less protest than one who meets it only on trip day.
Sizing traps to avoid with a Scottish Fold
Do not size down because a Fold looks small when curled up, since her curled silhouette hides her true width and length. Do not add a thick cushion that steals headroom, and do not trust a shop label without the interior dimensions, because medium means different things across makers. If your Fold is a larger male or a cat who is still filling out, choose the larger end of the range or step up a size rather than hoping she will squeeze in. A carrier that is slightly roomy still feels secure to a Fold who can brace her feet, while a tight one turns every bump into a struggle. In KinsLe, Family Sharing holds the Scottish Fold's exact carrier dimensions, pad choice, and door preference in one shared profile, so whoever drives her to the vet packs the carrier she already knows.