Gear & Trail
How to Fit a Dog Backpack: Measure, Adjust, Go
AlphaPak · Reviewed by our veterinary and formulation team · Updated August 26, 2026
Fitting a dog backpack takes two measurements: around the widest part of the ribcage, and around the base of the neck. Match them to the size chart, and if your dog lands between sizes, take the smaller one. Once it arrives, adjust the straps snug enough that two fingers still fit underneath.
How do you fit a dog backpack?
Two measurements and a chart — that's the whole job. Measure around the widest part of your dog's ribcage, just behind the front legs. Then measure around the base of the neck, where a collar sits. A soft tape measure works best, but a piece of string held up to a ruler does the same thing.
Skip the shortcuts. Some sites guess a size from your dog's weight, but dogs come in every shape, and a lean 50-pound pointer and a barrel-chested 50-pound bulldog need different packs. Measure your own dog and trust the numbers.
Read the size chart
Compare your two numbers to the chart:
| Size | Chest girth | Neck |
|---|---|---|
| Small | 17–22" | 10–14" |
| Medium | 22–27" | 14–20" |
| Large | 27–32" | 16–23" |
| X-Large | 32–42" | 22–30" |
Between two sizes? Take the smaller one. The EZ Fit™ straps take up the extra room, so a smaller pack adjusts up to fit. An oversized pack can't be cinched down far enough, and a loose pack shifts, slides, and rubs.
Adjust with the two-finger rule
When the pack arrives, put it on your dog and work through the straps. You want the pack snug enough to sit still, with enough room to slide two fingers between the strap and your dog. That's the balance: secure, and comfortable.
The EZ Fit™ buckles latch down to lock, and the leftover strap tucks into rubber loops so nothing flaps or works loose. All the adjusting takes about 30 seconds.
The sign your pack is too big
If a front strap keeps slipping on hikes, the pack is almost always a size too big — not broken. Recheck the girth measurement against the size you bought. Loading both saddlebags to the same weight matters too; a lopsided pack pulls itself sideways.
Still unsure between sizes? Send us your dog's measurements and we'll tell you which size we'd ship. And once the fit is dialed in, ease into the weight — here's how much a dog can carry.
Common questions
- How do I measure my dog for a backpack?
- Use a soft tape measure or a piece of string. Measure around the widest part of the ribcage, just behind the front legs, and around the base of the neck where a collar sits. Take the measurements yourself — weight and breed alone are not reliable, because dogs come in every shape.
- What if my dog is between two sizes?
- Take the smaller size. The EZ Fit™ straps take up slack, so a smaller pack adjusts up to fit. A pack that starts too big can't be cinched down far enough, and it will shift and slide on the trail.
- How tight should a dog backpack be?
- Snug, not tight. Adjust the straps until the pack sits still, then check that you can slide two fingers between the strap and your dog. That keeps the pack secure without pressing on their chest.
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