📐 Measure or estimate

Neck circumference (measured snugly where the collar will sit)

📏 Use a soft tape measure (or a string, then measure the string) around the neck where the collar normally sits, snug but not tight — like the two-finger test.

Collar type

Flat / buckle

Martingale

Chain / choke

Narrow head vs. neck (sighthound-type)

Greyhound, Whippet, Saluki, etc. — head is thinner than the neck

This is a growing puppy

Needs room to grow, plus regular rechecks

Recommended collar size

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Your neck input

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Collar type

This is a general sizing estimate. Collar sizing varies slightly between brands, so always check the specific product's size chart, and recheck the fit by hand once the collar arrives — you should be able to fit two fingers flat between the collar and your dog's neck.

🏆 Why this calculator is different

🔗Adjusts by collar type — flat, martingale and chain collars each fit differently; most calculators use one generic formula for all three.
🐕Sighthound / narrow-head safety check — flags when a martingale is strongly recommended instead of a flat collar, since narrow-headed breeds can slip a standard collar entirely.
📏Two sizing paths — measure the actual neck for best accuracy, or estimate from weight when you don't have a tape measure handy.
🐶Puppy growth awareness — flags when to buy an adjustable range and reminds you to recheck the fit as they grow.
✅Two-finger test built into the guidance, not just a bare number with no fit-check reference.
🔒No sign-up, no data stored — everything runs in your browser only.

❓ Frequently asked questions

How do I measure my dog for a collar?

Wrap a soft tape measure (or a string, then measure the string against a ruler) around the neck where the collar will sit, snug but not tight, then add roughly 2 inches (5 cm) for a comfortable, adjustable fit.

What's the two-finger rule for dog collars?

You should be able to slide two fingers flat between the collar and your dog's neck. If it's tighter than that, the collar is too small; if you can fit more than two fingers easily, it may be too loose.

Why do sighthounds need a martingale collar?

Breeds like Greyhounds and Whippets often have a neck that's wider than their head, which means a standard flat collar can slip off backward — a martingale tightens slightly when pulled, preventing escape without choking the dog under normal walking tension.

🐕‍🦺📏 Dog Collar Size Calculator