A collar that's too tight can cause discomfort, restrict breathing, or damage the trachea. Too loose, and your dog can slip straight out in a moment of excitement or fear. For small dogs with delicate necks, the fit of a collar isn't just important — it's the whole point.
Here's exactly how to measure your dog so their collar is safe, comfortable, and secure.
What you'll need
- A soft measuring tape — tailor's tape works best, flexible and accurate.
- Or a piece of string and a ruler, if you don't have measuring tape.
- Your dog, and a few high-value treats for cooperation.
- Optional: a helper, which makes measuring a squirmy dog much easier.
Step 1: Measure the neck
Wrap the measuring tape gently around the base of your dog's neck — where the collar naturally sits. This is usually the widest part of the neck, just above the shoulders and below the jawline.
Keep the tape snug but not tight — it should rest against the fur without pressing into the skin. Make sure it's level all the way around, not twisted or slanted, and note the measurement in centimetres, which is more precise for small dogs. If you're using string, wrap it around the neck, mark where it meets, then measure the string against a ruler.
Measure when your dog is standing calmly. Neck measurements taken while a dog is sitting or lying down can be inaccurate. If your dog's fur is very thick, press it down gently with the tape to measure against the skin.
Example: your Chihuahua's neck measures 22 cm.
Step 2: Apply the two-finger rule
Once you have the measurement, add space for comfort and safety. You should be able to slide two fingers — index and middle — comfortably between the collar and your dog's neck. Not one finger, which is too tight; not three, which is too loose. The collar should be snug enough not to slip over the head, but loose enough that it never restricts breathing or movement.
In practice: add 2–4 cm to your dog's neck measurement to account for the two-finger space.
Example: a 22 cm neck means an ideal collar size of 24–26 cm on the adjustment range.
Step 3: Check the adjustability range
Most collars have an adjustable range — for example 20–28 cm or 25–35 cm. Your dog's measurement should fall in the middle third of that range. This leaves room to tighten or loosen for weight changes, winter coats, or growth.
Avoid sizes where your dog's measurement sits at the very start or end of the range — collars at their adjustment extremes are more likely to fail, slip, or become uncomfortable.
Example: for a 22 cm neck, a 20–28 cm collar is ideal — 22 sits in the middle. A 25–35 cm collar would force the collar to its tightest setting, which isn't ideal.
Collar width: it matters for small dogs
| Dog weight | Recommended width | Notes |
|---|---|---|
| Under 2 kg | 0.8–1 cm | Ultra-lightweight, minimal bulk |
| 2–5 kg | 1–1.5 cm | Standard for toy breeds |
| 5–8 kg | 1.5–2 cm | Small breeds, slightly sturdier |
| 8–12 kg | 2–2.5 cm | Upper end of the small-dog range |
Too wide and a collar is heavy and can rub; too narrow and it can dig into the neck. For small dogs with tracheal sensitivity, stay at 1–1.5 cm maximum. One exception: dogs with very short necks, like Pugs or French Bulldogs, do better with a slightly wider collar (1.5–2 cm), which distributes pressure more evenly.
Special considerations for small dogs
Puppies
Measure weekly during rapid growth, roughly 8–16 weeks — puppies can outgrow a collar in under a week. Choose an adjustable collar, buy for current size rather than "to grow into," and consider a breakaway collar that releases under pressure if it catches on something.
Senior dogs
Weight fluctuates more with age, so check the fit monthly. Arthritic dogs can be sensitive around the neck — a wider, padded collar is more comfortable.
Flat-faced breeds
French Bulldogs, Pugs and Boston Terriers have shorter necks and respiratory sensitivity. Measure carefully — even slightly too tight can restrict an already compromised airway — and choose a wider collar (1.5–2 cm). Always walk these breeds on a harness, never a leash attached to the collar.
Long-haired breeds
Fluff adds bulk, so measure under the fur, against the skin. Re-check the fit after grooming, when the neck may appear smaller, and avoid collar designs that mat or tangle long fur.
Escape artists
Some small dogs — sighthounds and narrow-headed breeds like Italian Greyhounds — can slip a traditional collar. Consider a martingale collar, which gently tightens when pulled, or a step-in harness. If your dog has escaped a collar before, never rely on one alone for walks.
Testing the fit, and when to re-measure
Once the collar is on, run through five quick checks:
- Two-finger test — two fingers slide under easily, neither tight nor loose.
- Slip test — gently try to pull the collar over the head, with your dog's cooperation. It shouldn't come off.
- Movement test — your dog can eat, drink, turn their head and breathe normally without the collar shifting.
- Comfort test — watch for 15–30 minutes. Constant scratching at the collar, coughing or gagging, the collar rotating to the side, or red marks and rubbed fur all signal a poor fit.
- Hardware test — the D-ring should sit at the top of the neck, and the buckle should be secure but easy to fasten.
Re-measure puppies every 1–2 weeks during growth, and adult dogs every 3–6 months — or sooner after weight changes, grooming, seasonal coat changes, or illness. Re-measure immediately if you can no longer fit two fingers under the collar, if it slips over the head, if you notice coughing or breathing changes, or if there's any redness or hair loss around the neck.
Common collar fitting mistakes
- Guessing size by breed. A 4 kg Maltese and a 4 kg Chihuahua can have very different neck sizes. Always measure.
- Buying a collar to "grow into." Puppies slip out of oversized collars or catch them on objects. Buy for current size and adjust as they grow.
- Never re-checking the fit. Weight, fur growth and age all change it.
- Using the extreme end of the adjustment range. Always choose a size where your dog falls in the middle.
- Ignoring weight and material. Heavy hardware and thick materials are uncomfortable on a tiny dog — choose lightweight, proportional designs.
Choosing the material
Nylon — lightweight, durable, affordable, and easy to clean. Can fray over time. Good for everyday wear.
Biothane — waterproof, odour-proof, easy to clean, and very durable. Slightly heavier than nylon and more expensive; ideal for active dogs or wet climates.
Leather — classic and durable, softens over time, but needs occasional conditioning and can stiffen if it gets wet. Heavier — not ideal for dogs under 3 kg.
Rope or paracord — lightweight and stylish, though usually fixed-size and less adjustable. Good for casual wear.
Padded collars — extra comfort for sensitive necks, with a wider surface that distributes pressure. Best for senior dogs or those with neck sensitivity.
A note on walks
A collar is for identification, not leash attachment. Small dogs should never have a leash clipped to the collar for walks — it puts pressure on the delicate trachea. Use a harness instead. For the full picture of when each one is right, see our guide to choosing between a collar and a harness.
Measuring for a dog collar: your questions answered
Can I guess my dog's size instead of measuring?
No. Even within the same breed, neck sizes vary significantly, and an ill-fitting collar is a genuine safety risk. Always measure.
My dog's neck measures exactly between two sizes. Which should I choose?
Size up. A slightly larger collar can be tightened; a too-small collar can't be safely loosened.
How tight should a collar be?
Snug enough that it won't slip over the head, loose enough to fit two fingers comfortably underneath. You should be able to rotate it around the neck easily.
Can a collar damage a small dog's trachea?
Yes — especially if it's too tight, or if a leash is attached during walks. Small dogs are prone to tracheal collapse, which is why a harness is the right choice for walks.
My dog hates wearing a collar. What can I do?
Start with short sessions of 5–10 minutes paired with high-value treats, then gradually increase the time. Some dogs prefer specific materials — soft nylon or a padded design. If resistance continues, use a collar only when necessary and rely on a harness otherwise.
How do I measure a squirmy puppy?
Enlist a helper to hold and distract with treats, and measure during calm moments after play or meals. Using string is often easier — wrap, mark, then measure the string afterward.
Can I use a collar I already have to measure?
Only if it fits perfectly. Measure the existing collar at the length where it currently fits your dog, including the two-finger space, then compare to the sizing chart.
The bottom line
- Measure at the base of the neck — the widest part, where the collar naturally sits.
- Add 2–4 cm for the two-finger rule.
- Choose a collar where your dog's measurement falls in the middle of the adjustment range.
- Match the width to your dog's weight — 1–1.5 cm suits most small dogs.
- Re-measure regularly: puppies weekly, adults every 3–6 months.
- Use a harness for walks — a collar is for identification.
A well-fitted collar means safety, comfort, and peace of mind for both of you.
Explore our collar collection, selected for small dogs.
