How harness sizing works
Most harness brands size primarily by chest girth: the circumference around the widest part of the ribcage, just behind the front legs. This calculator uses commonly published general size ranges as a starting reference point.
Typical girth ranges
- XS: under 16 in
- S: 16-20 in
- M: 20-26 in
- L: 26-32 in
- XL: 32-38 in
- XXL: 38 in and up
Every brand sets its own exact size chart, and factors like coat thickness and harness style (step-in vs. overhead) change the right fit. Always check the specific product’s size chart and measure snugly (two fingers should fit under the strap) before buying.
Last reviewed August 2026