Dog apparel sizing is not standardized across the industry. A size Medium from one brand may be equivalent to a Large from another, and some brands use numbered sizing (8, 10, 12) while others use letter sizing (XS through XXL). The only reliable approach is to measure your dog and compare those measurements directly to the chart.
Most size charts list three to four measurements: neck, chest, back length, and sometimes belly girth. Focus on chest girth first — it's the measurement that causes the most fit problems when ignored. If a chart only shows weight ranges, treat that as a rough starting point and look for a brand that provides actual body measurements.
When your dog's measurements fall between two sizes, the right choice depends on the garment type. For structured jackets with closures, size up and use the adjustable straps to dial in fit. For knit sweaters with stretch, sizing down slightly is often fine. For pajamas and onesies, back length is usually the deciding factor — a garment that's too long will bunch and restrict movement.
Pay attention to breed-specific notes on size charts. Some brands call out that their sizing runs narrow for deep-chested breeds like Boxers or Dobermans, or that their back lengths run short for long-bodied breeds like Dachshunds. These notes are worth reading before you order.
If you're shopping in person, bring your measurements written down rather than relying on memory. Hold the garment up and check that the chest opening looks proportionate to your dog's girth measurement. A garment that looks obviously narrow on the hanger will be tight on your dog.
Finally, check the return and exchange policy before purchasing. Even with careful measuring, fit can be unpredictable with a new brand. A brand that makes exchanges easy is worth the extra consideration, especially for your first purchase.
General education only. This guide is not veterinary advice. For questions about your dog's health, behavior, or medical needs, consult a licensed veterinarian.
