A collar that's too tight can restrict breathing and damage the trachea. Too loose, and your dog slips out and gets lost. Getting the size right is one of the most important things you can do as a dog owner. Here's the complete guide.
How to Measure Your Dog's Neck
Use a soft measuring tape (or a piece of string you then measure against a ruler):
- Wrap the tape around the middle of your dog's neck — not the base, not the top, but the middle where the collar will sit
- Slide two fingers between the tape and the neck
- Read the measurement — this is your dog's neck circumference
- Add 1-2 inches to this measurement to get your ideal collar size
Example: Neck measures 14 inches → buy a collar in the 14-18 inch adjustable range.
The Two-Finger Rule
Once the collar is on your dog, you should be able to slide two fingers — not one, not three — between the collar and the neck. This is the universal fit test:
- Can't fit two fingers: Too tight — loosen or size up
- Can easily fit three or four fingers: Too loose — tighten or size down
- Two fingers slide in with slight resistance: Perfect fit
Collar Size by Breed Reference
| Breed Size | Typical Neck Size | Collar Size |
|---|---|---|
| Extra Small (Chihuahua, Yorkie) | 6-8 inches | XS: 6-10" |
| Small (Beagle, Pug, Shih Tzu) | 9-12 inches | S: 10-14" |
| Medium (Border Collie, Cocker Spaniel) | 13-16 inches | M: 14-18" |
| Large (Labrador, German Shepherd) | 17-20 inches | L: 18-22" |
| Extra Large (Great Dane, Mastiff) | 21-26 inches | XL: 22-28" |
Always measure your individual dog — breeds vary widely within size categories.
Puppies: Plan Ahead
Puppies grow fast. A collar that fits perfectly at 8 weeks may be dangerously tight at 12 weeks. Check collar fit every 1-2 weeks during the first 6 months. Adjustable collars that cover a wide range of sizes are ideal for growing puppies.
Different Collar Types and Sizing
Flat buckle collar: Standard everyday collar — use the sizing guide above.
Martingale collar: Has two loops — tightens slightly when pulled but can't over-tighten. The collar should be loose enough that you can't pull it over the dog's head when not tensioned.
Harness vs. collar: For dogs that pull, consider a front-clip harness instead of or in addition to a collar. Collars should always be worn for ID tags even if you walk with a harness.
When to Replace a Collar
- When the buckle no longer closes securely
- When the D-ring is bent or weakened
- When the material is frayed, cracked, or worn thin
- When your puppy outgrows it (check monthly)
Browse PawVault's dog collar and harness collection. All sizes available with free shipping on orders over $50.