How to Measure for Dog Collar Size? | The Two-Finger Test

For the full breakdown, see our best Dog Collar For Labrador guide.

Getting the right collar size is the difference between a comfortable walk and a choking hazard or an escape artist. The good news is the process takes less than a minute. Whether you are fitting a puppy who’s still growing or an adult dog, the method boils down to one accurate neck measurement and a simple fit check. This guide walks you through the steps and the common mistakes to avoid.

The Right Way To Measure Your Dog’s Neck

Use a fabric or soft tape measure for the most accurate reading. If you don’t have one, a piece of string, ribbon, or even an old leash works fine. Wrap it around your dog’s neck at the base, right where the collar naturally rests, which is typically the widest part of the neck. The tape should be snug but not tight, just touching the fur.

If you’re using a string, mark the point where the end meets the rest of the string, then lay it flat against a ruler to get the length in inches or centimeters. This base measurement is the number you’ll compare against a manufacturer’s size chart.

Use An Existing Collar For A Perfect Match

The most reliable way to match a new collar to an old one is to measure the current collar directly. Remove it and lay it flat on a surface. Measure from the center of the buckle (the bar where the prong goes through) to the hole you currently use for a buckle-style collar. This is the standard method that most brands, including those at PetSmart, reference in their sizing guides.

Don’t measure the collar end-to-end or include the buckle in your measurement. That will add extra length and lead you to buy a collar that’s too big. This measurement gives you the exact “worn length,” which is more precise than a neck measurement alone.

Why The Two-Finger Rule Fixes Most Fitting Problems

Neck measurements alone don’t tell the whole story. The final check is all about fit. After you put the collar on, you should be able to slip two fingers comfortably between the collar and your dog’s neck. This is the practical rule used consistently across manufacturers, including GoTags and others. It ensures the collar is tight enough to prevent slipping off but loose enough to avoid discomfort or breathing restriction.

A collar that is too tight can cause skin irritation or make it hard for a dog to swallow. A collar that is too loose can easily slip over the head, especially with breeds that have narrow heads. If you can fit more than two fingers, tighten it. If you can’t fit even one finger, it’s too tight and you need a larger size.

What About Size Charts And Special Collar Types?

Always defer to the specific brand’s size chart, as sizing can vary significantly between manufacturers. While a US chart might list a Medium for a 16-inch neck, a UK-based chart like the one from GoTags might suggest a Small. Your best bet is to rely on your base neck measurement and compare it directly to the chart of the collar you want to buy.

Specialty collars also have different rules. For a prong or pinch collar, the measurement is taken right behind the ears, higher up on the neck than a standard flat collar. For chain training collars, the fit is usually measured mid-neck, similar to a flat collar. If you’re in doubt, check the manufacturer’s specific instructions, as some brands have unique endpoints for side-release buckles versus traditional buckles.

If you’re shopping for a larger breed like a Labrador, you’ll want a collar that fits their robust neck.

Note: These ranges are for reference only. Always check the specific brand’s chart before purchasing.

Frequently Asked Questions

Should I add extra length to my dog’s neck measurement?

Most modern size charts already account for the buckle and overlap, so you don’t need to add extra room. However, some manufacturers recommend adding 1–2 inches, especially for puppies or dogs between sizes. The safest approach is to follow the specific brand’s instructions on their size chart and use the two-finger rule for the final fit.

Why does my dog’s collar seem too big even when the neck measurement is right?

This usually happens when the collar is measured end-to-end, which incorrectly includes the buckle’s length. Always measure from the center of the buckle to the hole in use. Also, make sure you are measuring at the base of the neck, not higher up under the ears, which would give a smaller reading.

How often should I remeasure my dog’s neck?

For adult dogs, remeasure every 6–12 months, as weight changes can affect neck size. For puppies, check the fit every few weeks during growth spurts, as they can outgrow a collar quickly. A simple two-finger check each month will help you know when it’s time to size up.