MEASURE FIRST. CHECK THE PRODUCT.
Dog Collar Size Calculator
Find the reference sizes that include your dog’s neck measurement, then learn what to check on the actual collar. For ordinary adjustable flat collars.
Adjustable flat collars
Start with their neck.
One measurement. A clearer range to look for.
The interactive calculator requires JavaScript. The sourced reference chart and instructions below are available without it.
Calculating saves or sends nothing. Saving to My Dog is optional.
Optional · Use My Dog measurements
Choose a dog, then apply each compatible measurement. This never calculates automatically. Saving is a separate action.
Opening this panel reads saved profiles from this browser. There is no account or cloud sync. Anyone using this browser can access them. Manage My Dog profiles.
JavaScript enables local profiles. You can use the measuring instructions below without it.
Recheck after growth, weight or posture changes, and before purchase. A save date does not tell you when a measurement was taken.
REFERENCE GUIDANCE · NOT A PRODUCT MATCH
Your collar sizing guidance
Let the measurement lead.
Enter your dog’s neck circumference to see every matching category in this retailer reference.
A size label is a starting point. Your chosen product’s chart determines its size.
Your dog’s measured neck
Using PetSmart general collar reference
Percentages show position within a reference interval, not physical fit or safety.
We compare the unrounded measurement. A “≈” means a displayed value is rounded.
See the source and calculation methodSize labels vary by brand and product. This is a disclosed retailer reference, not a universal sizing standard or a verified product match.
Recovery equipment has its own endpoints: use the recovery cone guide for neck circumference at the cone attachment plus neck-to-nose reach.
GET THE MEASUREMENT RIGHT
How to measure your dog’s neck
Record the neck circumference first. Selecting a size and adjusting the collar are separate steps.
- Let your dog stand comfortably in a natural position.
- Find where their everyday flat collar normally rests. Check the product’s measuring location if specified.
- Wrap a flexible measuring tape around that part of the neck.
- Keep it close to the coat without squeezing the neck or leaving a loose loop.
- Read and record the circumference with its unit. Measure again to check; do not add extra length for this calculator.
- Use the individual manufacturer’s measuring and fitting instructions when choosing and adjusting a collar.
A REFERENCE, WITH ITS SOURCE
Dog collar size chart
These are the published neck ranges from PetSmart’s general sizing chart. The centimeter endpoints are exact conversions of the source’s inches. They describe this reference only; individual collars can use different labels and ranges.
| Reference size | Neck in inches | Neck in cm |
|---|---|---|
| XX Small | 6 in – 8 in | 15.24 cm – 20.32 cm |
| Extra Small | 8 in – 12 in | 20.32 cm – 30.48 cm |
| Small | 10 in – 14 in | 25.4 cm – 35.56 cm |
| Medium | 14 in – 20 in | 35.56 cm – 50.8 cm |
| Large | 16 in – 26 in | 40.64 cm – 66.04 cm |
| Extra Large | 24 in – 30 in | 60.96 cm – 76.2 cm |
All endpoints are included in the calculation. Overlapping categories are deliberate. We use only the chart’s neck ranges, not its breed or weight examples.
FROM A NUMBER TO AN ACTUAL COLLAR
How to choose the correct collar size
- 01
Measure the neck
Keep your original measurement and unit. A breed guess or an old collar’s total length is not a substitute for the dog’s neck circumference.
- 02
Read the product’s range
Look for a manufacturer-listed neck-size range that includes the measurement. Confirm that the chart describes a neck range rather than an end-to-end collar length, and follow its measuring method.
- 03
Adjust and check the fit
Fasten and adjust according to the product’s instructions. Check for pressure, rubbing, movement, and whether it can easily slip over the head. A matching chart value does not complete this check.
WHEN RANGES OVERLAP
Between collar sizes?
Both labels may appear because this chart’s intervals overlap. At 14 inches, for example, Small ends and Medium begins; both are shown.
Recheck your measurement, then compare the particular product’s adjustment range, collar width, and fitting instructions. Neither the larger nor the smaller label is automatically the right choice. Ask the manufacturer if its guidance leaves the choice unclear.
GROWING DOGS
Puppy collar sizing
Measure your puppy’s current neck. Recheck it and the collar’s fit regularly as they grow, and replace a collar when its adjustment range no longer works.
Future growth is not a reason to fasten a collar loosely today. This calculator does not predict growth or add a puppy allowance.
Why breed and weight are not enough
Dogs of the same breed or weight can have different neck proportions. Those details can give context, but they cannot locate your individual dog’s neck within a product’s adjustment range. This tool asks only for the measurement it uses.
HOW THIS RESULT IS WORKED OUT
Sources and sizing method
We compare the unrounded neck circumference with each PetSmart reference interval and return every matching category. Both ends count. No allowance, ranking, growth prediction, or extra category is added. Values outside all six ranges receive an outside-chart explanation.
The marker uses (measurement − minimum) / (maximum − minimum). “Near the lower end” or “near the upper end” means the outer 10% of this reference interval, a display convention rather than a manufacturer’s fit margin. A rounded display never changes the comparison.
- PetSmart sizing charts supplies the six reference neck ranges above.
- Ruffwear Front Range and Hi & Light provide product-specific comparison context. Their charts demonstrate why one reference cannot stand in for every collar. We do not calculate a Ruffwear product match.
- AKC’s measuring guide informs the neck-measuring location and the need to consult a product’s chart.
- AKC’s collar guidance informs practical fitting checks. We keep these separate from the measured circumference.
All five sources were checked October 8, 2026. Published charts can change. This reference cannot account for collar construction, individual anatomy, or measurement error; check the current product instructions before selecting a size.
HELPFUL ANSWERS
Collar sizing questions
What size collar does my dog need?
Start with their measured neck circumference. This calculator shows every category that contains it in the disclosed retailer reference. Then compare that measurement with the neck-size range of the particular collar you want to buy. Its label may differ from this chart.
Should I add two inches to the neck measurement?
This calculator adds no length. Enter the measured circumference without an automatic allowance. Follow the chosen product’s measuring and adjustment instructions; adding the same amount to every dog can give a misleading result.
Why does the calculator show two sizes?
The published reference ranges overlap. A measurement can belong to more than one category, including at a shared endpoint. We show all of them instead of selecting a larger or smaller label without product-specific evidence.
What does the marker on the range mean?
It shows your measurement’s position between that reference range’s minimum and maximum. The percentage is not a fit score. Near an edge, recheck your measurement and the actual product’s adjustment range and instructions.
What if my measurement is outside the chart?
A positive measurement can be valid even when this reference does not cover it. We do not clamp it or invent another size. Look for an individual product chart that includes your dog’s measurement, or ask its manufacturer for help.
Can I use this for a martingale or training collar?
This tool is for ordinary adjustable flat collars. Martingale, slip, prong, electronic training, medical, and specialized restraint collars need their own fitting instructions and are outside this calculator’s scope.