Why two brands’ "Medium" are different dogs

The myth of the standard medium harness

There is no governing standards body for dog equipment. In human apparel, international organisations set clear dimensional standards for sizing. In pet gear, manufacturers choose their own grading rules, size labels, and measurement boundaries. A Medium harness from one brand often bears no physical resemblance to a Medium harness from another.

This lack of industry standards means dog harness sizes not standard across the market. One manufacturer might split its entire fit range into five sizes, while another splits a similar range into nine. A dog positioned neatly in the middle of one brand's range may fall between sizes or sit at an extreme edge in another.

Comparing size distribution across major brands

To understand why size labels fail, examine how different manufacturers divide their product lines across chest girth measurements.

Consider five established harness lines:

• Julius-K9 IDC Powerharness: Spans 29 to 138cm across 9 sizes. It publishes weight guidance alongside chest measurements.
• PetSafe: Covers 28 to 119cm across 8 sizes. It mostly publishes weight figures alongside dimensions.
• Ruffwear: Spans 23 to 107cm across 7 sizes. It relies purely on girth and publishes no weight guidance.
• Kurgo: Covers 30 to 94cm across 5 sizes. It publishes weight recommendations.
• Blue-9: Spans 33 to 91cm across 5 sizes. It uses girth only and publishes no weight guidance.

Notice the structural differences. Kurgo and Blue-9 both use five sizes, but their total coverage differs by 3cm at the lower end and 3cm at the upper end. Blue-9 spreads five sizes across a 58cm span. Kurgo spreads five sizes across a 64cm span. Consequently, the grading increment between each size is entirely different.

When a brand like Julius-K9 divides its range into nine sizes, the step between each size is much narrower. A dog measured at 60cm girth sits in a completely different relative position within a 9-size scale compared to a 5-size scale.

Why weight recommendations create confusion

Many owners rely on weight when ordering gear. This is a primary source of sizing errors. Body mass does not dictate chest circumference. A deep-chested Greyhound and a barrel-chested French Bulldog might weigh the exact same amount, but their girth measurements require completely different harness geometries and strap lengths.

Furthermore, weight data is incomplete across the industry. Ruffwear and Blue-9 publish no weight guidance whatsoever. They rely exclusively on chest girth. Web pages that print a recommended size for every brand based solely on a dog's weight are simply guessing.

The house position at FurPick is straightforward: girth is the measurement that decides fit. Weight is only ever a tie-breaker when a dog sits precisely on the boundary between two sizes. You can check your dog's exact measurements against multiple brand algorithms using the sizing tool.

What happens when you reorder across brands

Switching brands requires a complete reset of your sizing assumptions. Assuming your dog will wear a Medium in a new brand because their previous harness was a Medium frequently leads to an improper fit.

When reordering from a new brand, ignore the letter label entirely. Look only at the lower and upper girth boundaries for that specific model. If your dog's chest measures 62cm, that figure corresponds to different labels across manufacturers:

• In a 5-size system spanning 30 to 94cm, 62cm sits near the boundary of the middle sizes.
• In a 9-size system spanning 29 to 138cm, 62cm sits in a much narrower, specific size tier.

Before switching brands, check the conversion chart to compare equivalent chest boundaries rather than arbitrary letter codes.

How to measure for reliable harness selection

To bypass unreliable size labels, measure your dog accurately using a flexible tape measure.

First, locate the widest part of the ribcage. Place the tape measure behind the front legs, wrapping around the widest part of the chest. This is the girth measurement.

Second, keep the tape snug. The tape should sit flat against the coat without depressing the skin or muscle structure.

Third, record the measurement in centimetres. Centimetres provide greater precision than inches when comparing narrow brand increments.

Finally, check strap adjustability. Ensure your dog's girth falls comfortably within the minimum and maximum range of the target size, leaving room for seasonal coat changes.

Frequently asked questions

Why do dog harness sizes differ between brands?

There is no official standards body for pet gear. Each manufacturer designs its own sizing scale, choosing how many size tiers to offer and where to set the minimum and maximum girth boundaries across its product line.

Can I choose a dog harness size based on weight alone?

No. Chest girth determines fit. Weight does not account for body shape or chest depth. Furthermore, brands like Ruffwear and Blue-9 publish no weight guidance, meaning weight-based selection for those brands relies on guesswork.

What is the most important measurement for a dog harness?

Chest girth is the primary measurement. Measure around the widest part of the ribcage, just behind the front legs. Use weight only as a secondary tie-breaker if a measurement falls exactly between two sizes.

Why do some brands have five sizes while others have nine?

Manufacturers select different grading increments for their product ranges. A brand with nine sizes offers narrower jumps between sizes for a precise fit, while a brand with five sizes uses wider adjustment ranges per harness.