How to Fit a Dog Pack for Hiking | Snug, Stable, and Safe

Fitting a dog pack for hiking is the difference between a happy trail partner and a dog that’s rubbing raw or struggling to breathe. The right fit is snug, stable, and high on the rib cage—never sagging onto the abdomen. Here’s the exact process for measuring, adjusting, and loading a pack that stays put on the trail.

Measure Your Dog for a Pack

The primary measurement for any dog pack is the chest girth: the widest part of the rib cage, just behind the front legs. Use a soft measuring tape and keep it snug but not tight while your dog stands.

Some manufacturers, like K9 Sport Sack, also require neck girth and back length—measured from the start of the collar to the base of the tail. Adventure Barx packs use both chest and length, with a Medium fitting an 18–25 in chest and Large a 21–28 in chest. Always check the specific size chart for the pack you’re buying, because sizing varies by brand.

If your dog falls between sizes, guidance conflicts. Ruffwear’s chart, for example, lists a Small at 22–27 in chest and a Medium at 27–32 in. The safest approach: follow the manufacturer’s chart for the exact pack, and prioritize a snug, nonrestrictive fit over a loose one.

The Step-by-Step Fitting Process

Fit the pack empty, before any weight goes in. Start with the chest or neck strap first, then tighten the belly and side straps. The field rule is two fingers under each strap—two to three for the neck area on some guides.

1. Measure chest girth at the widest point behind the front legs.
2. Match that number to the manufacturer’s size chart.
3. Put the empty pack on and adjust all straps.
4. Check that the pack sits high and even on both sides, with the front edge clear of the shoulders and armpits.
5. Slip two fingers under each strap and confirm your dog can breathe and move normally.
6. Let the dog wear the empty pack around the house or on a short walk before any hike.

REI’s expert advice stresses that a correctly fitted pack should not slip, twist, or sag, and it should sit on the rib cage—not slide onto the soft abdomen. The pack should also not extend past the last rib on the side, which can cause chafing.

When the pack is on, watch your dog move. If they hesitate, change gait, or try to roll the pack off, the fit is wrong. Recheck the fit during the hike, especially after the first hour and on descents, because straps loosen and packs shift.

How Heavy Can a Dog Pack Be?

The common upper limit is 25% of your dog’s body weight, including the pack and its contents. Ruffwear states this directly, using the example of a 45-pound (20-kg) dog carrying no more than 11.25 pounds (5 kg) total. REI calls 25% a rough guideline, since age, size, and strength change what’s safe.

More conservative guidance exists. At least one manufacturer recommends starting at no more than 10% of body weight, especially for younger or less conditioned dogs. When in doubt, start lighter and build up gradually.

Balance the load evenly in both saddlebags. An unbalanced pack causes rotation, chafing, and balance problems that tire your dog fast and can cause injury over time.

Signs the Pack Fit Is Wrong

• Too tight: restricted breathing, reluctance to move, or shoulder stiffness.
• Too loose: the pack slips sideways, twists, or slides onto the belly.
• Chafing: rub spots or redness under the straps or where the pack meets the ribs.
• Pack rotation: the whole pack swivels around the body, which means straps are uneven or the load is unbalanced.

Check for all of these after the first hour of any hike. The pack should feel like a well-fitted harness: present, but not restricting. If you’re ready to buy a model, our tested roundup of the best dog packs compares top options side by side.