What Size Collar for Australian Shepherd? | Neck Size Matters

The right collar size for an Australian Shepherd isn’t a “large” or “medium” label — it’s a precise neck measurement. Aussies are working dogs with thick coats and sturdy necks, which makes guessing especially unreliable. Adult standard Australian Shepherds typically fall in the 16–22 inch range, and the choice within that band depends on whether your dog is still growing or fully grown.

How To Measure An Australian Shepherd’s Neck Properly

If you measure only one thing before buying a collar, make it the neck girth — not the chest or weight. Dry the coat or have your dog stand comfortably, then place a soft measuring tape where the collar will actually ride: high on the neck, right behind the ears and just above the shoulder line.

A few fit rules matter more than any brand chart:

• Keep the fit snug but not tight, you should be able to slip two fingers between the fabric and the neck (the standard safety check).
• Don’t measure over thick fur; compress the neck, not the coat, and you’ll get a truer number.
• If your Aussie is still growing, pick the larger of two close sizes so you can adjust it outward as the neck widens.
• For a fully grown dog between sizes, the smaller option is usually right.

If you’re confident your dog is fully grown, but the measurement falls between sizes, one common recommendation is to choose the smaller size for a secure fit. A too-loose collar can slip off during a walk; a too-tight one can rub or press on the throat.

Size Ranges For Australian Shepherds

Because Australian Shepherds come in standard and miniature sizes, checking the neck measurement range is the most reliable path. Here’s what the common sizing charts point to:

These ranges reflect widely used sizing charts and are a great starting point — but your tape measure tells the real story.

For a carefully vetted selection of collars that fit these neck ranges, see our roundup of the best collars for Australian Shepherds to compare top-rated options.

Common Fit Problems To Avoid

A whip-thin collar on a neck that measures 20 inches will sit too high and pull against the windpipe, especially when a lively Aussie lunges after a squirrel. Too loose, and the collar works forward and rides over the ears or slips off altogether.

This is why measuring the current neck, rather than relying on the dog’s age or weight, solves most problems before they start. Re-measure your Aussie’s neck every couple of months during the first 18 months, as the body — and neck — continues to fill out.

If you’ve measured a young adult that’s still filling out or an adult with a very thick coat, size up slightly and use the adjusters to dial in the fit. The two-finger rule remains the final check, no matter which size you land on.