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Puppies grow fast. A collar that fits perfectly on a 10-week-old Labrador can be dangerously tight six weeks later. Choosing the right collar size for a growing puppy is less about picking one perfect size and more about measuring correctly, choosing an adjustable design and checking fit every week. This guide explains how to measure, how tight is too tight, how growth rates differ by breed size, and when to move on to the next collar.
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Quick answer: Our top pick in 2026 is the Toy (under 12 lb adult) — our #1 rated choice. See the full ranked comparison, alternatives and buying advice below.
How to Measure Your Puppy’s Neck
- Use a soft, flexible tape measure.
- Measure around the middle of the neck, where the collar will sit, not at the base near the shoulders.
- Keep the tape snug but not tight.
- Add about 1 inch for small puppies and about 2 inches for medium and large puppies.
If you do not have a tape measure, use a piece of string, mark it, and measure the string against a ruler.
The Two-Finger Rule
See also: How to Pick a Heating Pad for an Arthritic Senior Dog • How to Transition a Picky Cat to a New Food
Once the collar is on, you should be able to slide two fingers flat between the collar and your puppy’s neck. For toy breeds, one finger may be more appropriate. If you cannot fit fingers under it, the collar is too tight. If the collar can slip over your puppy’s head when you pull gently forward, it is too loose.
Choosing a Size Range
Most collars list an adjustable range, for example 10 to 14 inches. Choose a collar where your puppy’s current measurement falls in the lower part of the range, leaving room to grow.
| Expected adult size | Typical puppy neck at 8-12 weeks | Growth pace | How often to check fit |
|---|---|---|---|
| Toy (under 12 lb adult) | About 6-9 inches | Mostly done by 9-10 months | Weekly |
| Small (12-25 lb) | About 8-11 inches | Mostly done by 10-12 months | Weekly |
| Medium (25-50 lb) | About 10-13 inches | Mostly done by 12 months | Twice a week in rapid growth |
| Large (50-90 lb) | About 12-15 inches | Can grow until 15-18 months | Twice a week in rapid growth |
| Giant (90 lb+) | About 14-17 inches | Can grow until 18-24 months | Twice a week |
These ranges are approximate; always measure your own puppy.
What Type of Collar Works Best for Puppies
Adjustable flat collars
A lightweight, adjustable flat collar with a buckle or quick-release clip is the most common choice. Look for a wide adjustment range and soft material.
Breakaway collars
Breakaway collars release under pressure, which can reduce the risk of strangulation if the collar snags. They are useful for wearing ID at home but are not intended for leash walking; use a harness or regular collar for walks.
Harness for walks
Many trainers and vets recommend a well-fitted harness for walking puppies, especially small breeds and those that pull, to avoid pressure on the neck. The collar can then carry ID tags.
Avoid for puppies
Choke chains, prong collars and other aversive tools are not recommended for puppies. Talk with a qualified trainer if you are having leash-walking problems.
Weekly Fit Check
- Do the two-finger test.
- Look for rubbing, redness or hair loss under the collar.
- Adjust the collar as needed.
- When the collar is at its largest setting and still fits snugly, it is time for the next size.
Safety Tips
- Remove collars during crate time or unsupervised play with other puppies, where collars can snag on crate wire or another dog’s teeth, unless using a breakaway design.
- Keep ID tags up to date and make sure your puppy is microchipped.
- Check the collar hardware for wear.
When to See Your Vet
If you notice skin irritation, hair loss, wounds or swelling under the collar, remove it and contact your vet. A collar that has become embedded in the skin needs urgent veterinary care.
FAQ
How many collars will my puppy need?
Many small-breed puppies need two, while large and giant breeds may need three or four before reaching adult size. Adjustable collars reduce how often you need to buy new ones.
Should my puppy wear a collar all the time?
A properly fitted collar with ID is useful, but remove it in the crate and during rough play unless it is a breakaway style. Always supervise young puppies.
Bottom Line
Measure your puppy’s neck at the middle, add 1 to 2 inches, choose an adjustable collar with room to grow, and use the two-finger rule to check fit every week. Large breeds grow for longer and need more frequent adjustments. Pair the collar with a harness for walks, keep ID current, and remove the collar during crate time or unsupervised play.
Ready to decide? Our #1 pick for 2026 is the Toy (under 12 lb adult).
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