How to Measure Dog Collar Size? | Neck Tape To Collar Fit

A collar that’s too tight chokes, and one that’s too loose slips off during a walk. Getting the right size means measuring the dog’s actual neck, not guessing by breed or weight. The process takes about 30 seconds with a flexible tape measure, or a phone charger cable and a ruler. This guide covers the three ways to get that number, the standard size chart that most brands follow, and the mistakes that throw the fit off by inches.

What You Need Before You Measure

Gather one of these measuring tools — the most accurate is a flexible tailor’s tape (the soft cloth kind used for sewing), but you can substitute a phone charging cable, a piece of string, or even a shoelace. A metal tape measure won’t bend around the dog’s neck properly. You’ll also write down the measurement in inches and open the brand’s specific size chart to check it against.

Method 1: Measure With A Flexible Tape Measure (Most Reliable)

This method gives the cleanest result in one step. Use a fabric sewing tape — the kind that bends and stays where you put it.

1. Wrap the tape around the widest part of the dog’s neck, which is usually just below the jawline and behind the ears.
2. Pull the tape snug — not tight enough to indent the fur, not loose enough to sag. It should sit flush against the coat the way a collar will.
3. Slide one finger between the tape and the neck. If it slides in with light resistance, the fit is right.
4. Read the number where the end of the tape meets the scale. That measurement in inches is the collar size you need.

The dog’s head should be in a neutral, standing position — not looking up or down, which changes the neck circumference.

Method 2: Measure With String Or A Phone Cable (No Tape Available)

This is the backup method for anyone who doesn’t own a sewing tape.

1. Take a phone charging cable, a piece of string, or a shoelace and hold one end against the dog’s neck at the widest point.
2. Wrap it around the neck, snug enough to fit two fingers between the cable and the skin.
3. Pinch the spot where the cable meets its starting end with your thumb and forefinger.
4. Release the cable from the dog and lay it flat against a ruler or a metal tape measure. Measure from the starting end to the pinch point.

Write that number down. This method introduces a little more error than a tailor’s tape, so measure twice, especially if the string stretched while you wrapped it.

Method 3: Measure The Dog’s Current Collar (If You Have One That Fits)

You can size a new collar from the old one, but only if you measure the right way.

1. Remove the existing collar and lay it flat on a table, buckle end to adjustment holes. Stretch it out so the material isn’t folded.
2. Measure from the center of the buckle — the tongue of the buckle — to the adjustment hole the dog has been wearing it on. That is the correct length.
3. Do NOT measure end to end (buckle tip to the farthest hole). That adds one to two inches of error and guarantees a loose fit.

The number you get is the collar size you should order. If the old collar is stretched, frayed, or heavily worn, the tape-measure method is safer.

Dog Collar Size Chart: Standard Ranges

Most brands follow these ranges, but always check the individual brand’s chart before ordering — Wild One, Modern Icon, and The Black Dog all have slight differences. The measurement below is a starting reference.

Find your dog’s measurement in the left column, then choose the corresponding size.

How To Pick The Right Size When The Dog Is Between Sizes

If your dog’s neck measures 15.5 inches and the chart jumps from 14″ to 16″, the right call depends on the dog’s age. For a puppy or young dog who hasn’t finished growing, choose the larger size and plan to re-check the fit every few weeks.

Special Sizing Rules For Prong, Chain, And Slip Collars

These collar types size differently than flat buckle collars because they must slip over the head. Herm Sprenger’s sizing guide explains the specific adjustments:

• Prong collars: Measure behind the ears (the narrowest part of the head the collar must pass over). Then add about two inches to that number for the collar length.
• Chain collars (choke chains): Measure mid-neck, where the collar will rest, then add two to three inches so the chain slips over the dog’s head easily.
• NeckTech / no-assembly collars: Use the actual neck measurement — these collars don’t have a separate assembly chain that adds length.

For dogs with very large heads compared to their necks — Pitbulls, Mastiffs, Bulldogs — measure the widest part of the head (around the skull behind the ears) and use that measurement for chain-style collars, or the collar won’t slip on at all. If you’re looking for a comfortable, well-rated buckle collar for a broad-headed breed, check our tested roundup of collars for bulldogs.

Common Sizing Mistakes That Ruin The Fit

Most sizing errors come from three habits that feel right but aren’t:

• Measuring the old collar end to end. This adds one to two inches. Always measure from the buckle center to the current hole.
• Relying on an old collar as the only guide. Leather stretches, nylon frays, and buckles loosen.
• Pulling the tape too tight or leaving it too loose. The one-to-two finger rule exists for a reason. Too tight is a choking risk; too loose lets the dog back out of the collar.

Also account for seasonal changes. A dog that swims heavily in summer or grows a thick winter coat can fluctuate by half an inch to an inch. If the collar fits perfectly in August, check it again in January before the fit becomes a problem.

Tips For Measuring A Wiggly Dog

A dog that won’t hold still makes any measurement hard. Distract with a treat held at nose level so the head stays neutral. If the dog squirms, the phone-charger method works better because you can wrap the cable and release it quickly. Measure twice on a calm dog; three times on a wiggly one. If the two measurements differ by more than a quarter inch, go with the larger one and check the fit against the size chart’s middle range.

Collars For Bulldogs And Broad-Headed Breeds: The Size Break

Bulldogs, French Bulldogs, Boston Terriers, and similar brachycephalic breeds have heads significantly wider than their necks. That means a standard neck measurement works for a buckle collar, but a prong or slip collar sized to the neck won’t go over the head. Measure the widest part of the skull (behind the ears) and add two inches for chain collars, or use a breakaway-style buckle collar sized to the neck measurement.

Checking The Fit After You Buy

Once the new collar arrives, put it on the dog and do the two-finger test. You should be able to slide two fingers flat between the collar and the dog’s neck — one finger for a snug working collar, two for a relaxed everyday collar. The collar should rest high on the neck, just behind the ears, not down near the shoulders where the dog can slip out of it. If you can pull the collar over the dog’s head from the front, it’s too loose. If you can’t fit one finger under it, it’s too tight.