Choosing a comb length is really two decisions: what coat is this, and how short can that coat safely go. Get the first wrong and the second does not matter — which is why the most important section of this guide is the one telling you not to clip at all.
Work out which coat you have
Single coat
One layer of hair that keeps growing, like human hair. Poodles, bichons, maltese, most doodles, yorkies, shih tzus. It mats rather than sheds, and it needs cutting — a single-coated dog left uncut for a year is a welfare problem, not a fashion statement. These are the coats clippers were designed for.
Double coat
A coarse outer guard layer over a dense, soft undercoat. Huskies, malamutes, akitas, chows, german shepherds, most collies, corgis, golden retrievers, labradors. It sheds seasonally instead of growing continuously.
Wire coat
Harsh, bristly outer hair. Wire fox terriers, schnauzers, border terriers, airedales. Traditionally hand-stripped rather than clipped; clipping is fine for a pet, it simply softens the texture and dulls the colour over time.
Short and smooth
Beagles, staffies, dalmatians, boxers. These need almost no clipping at all — paws and sanitary areas only.
The double-coat rule
Do not shave a double coat. This is the one instruction in all three of these guides that we would ask you to treat as absolute.
The undercoat is insulation and it works in both directions: it keeps heat in during winter and keeps radiant heat out during summer. The guard coat sheds water and blocks sun. Clip through both and you remove the animal's temperature regulation and its sunburn protection at the same time, which is the opposite of the cooling effect most owners are aiming for.
Regrowth is the other half of the problem. Undercoat grows back faster than guard hair, so a shaved double coat often comes back as dense fluff with the coarse protective layer patchy or missing. On older dogs it sometimes does not come back properly at all. Groomers call it clipper alopecia, and there is no reliable fix.
What to do instead: rake the undercoat out. An undercoat rake or a deshedding tool pulls the dead fluff without cutting the guard hair, and a thoroughly raked double-coated dog is dramatically cooler than an unraked one while keeping every bit of its protection. Use the clipper on that animal only for paws, feathering, the sanitary area and any genuinely matted patch you cannot save.
Length by length
- 25 mm and 20 mm — a tidy, not a haircut. Evens out a doodle or a spaniel without changing the silhouette. The safest choice if you are unsure, and impossible to regret.
- 16 mm — a proper winter length for curly and wavy coats. Still enough coat to protect skin and to hide an uneven pass.
- 12 mm — the default for a first home groom on almost any single coat. Neat, easy to maintain, forgiving of a wobbly line.
- 9 mm — a tidy summer length for terriers, spaniels and cockapoos. Roughly a six-to-eight-week cut before it needs redoing.
- 6 mm — a short, low-maintenance body clip. Practical for a dog that swims or rolls in things. On thin-skinned or pale dogs, apply sunscreen to the belly and nose bridge for the first fortnight.
- 3 mm — short. On most dogs you will see skin colour through the coat. Use it deliberately, not because you were unsure and went shorter to even something out.
- Bare blade, 0.8 mm — paw pads and sanitary areas only. Never a body length.
Cats
Cats are a different animal in every sense. Feline skin is roughly a third the thickness of canine skin and it moves freely over the muscle beneath, so it lifts into a blade far more readily.
- Never go below 6 mm on the body, and use a guide comb at all times. Nicking a cat is easy and heals slowly.
- Use low speed. 4,200 rpm is quieter and gentler, and cats respond to both.
- Work in small areas. The base of the tail and the backs of the thighs mat first on long-haired cats and are usually the only places that genuinely need clipping.
- Never clip whiskers or the hair inside the ears. Both are sensory equipment.
- Short sessions. One area a day is a perfectly good pace.
A severely matted cat is a veterinary job, not a home job. Mats pull on skin continuously and can hide sores underneath; a vet can sedate and clear it in one session without a fight.
Repeating a cut you liked
Write down what you used. The combs are numbered for exactly this reason, and "9 mm body, 12 mm legs, bare blade on the pads" is all the note you need to reproduce a good result six weeks later instead of guessing.
If you want the same look but the coat has grown unevenly, go up a length rather than down. Longer combs blend an uneven coat; shorter combs expose every place the previous cut wandered.
Blending body and legs
Legs almost always look better one length longer than the body. Clip the body at 9 mm and the legs at 12 mm and the dog reads as deliberately groomed. Clip everything at one length and it reads as shaved, particularly on breeds with feathering.
Where the two lengths meet, work the longer comb upwards into the shorter area with short flicking strokes rather than a hard stroke. That feathered transition is the difference between a home groom and an obviously home groom.