Dog backpacks are a great invention for SO many reasons. If you're going on walks or hikes, life is simpler when your dog can carry their own gear. In addition, there are many dogs such as Huskies, Malamutes, Mastiffs and many of the large dog breeds, who were bred to carry or haul - they love being able to do their job. And if you have a high-energy dog that's hard to tire out, having them carry a pack with weight in it can get the job done much faster and have them feeling really good about themselves. It really is true that most dogs love to work - they're happy when they can carry their own weight (yes - that's a joke).
As a general rule, dogs can carry up to one quarter of their body weight without strain. Breeds like Huskies and Malamutes who were specifically bred to haul can easily carry up to one third of their body weight without breaking a sweat.
Backpack sizes are based on the weight of your dog. It's important to measure your dog before purchasing a dog pack to get the best and safest fit. Typically, you measure their girth (from behind the shoulder and around the belly behind their elbows) and the length of their spine. Make sure the design doesn't restrict movement and that most of the weight will be carried near their shoulders - not on the their backs. Their pulling strength comes from the shoulders, and you don't want weight far down their backs or they can strain their spine - not a good thing.
Packs that have spine support built into the design are best to help protect your dog's back. This is especially important if you're in an environment where your dog will be twisting and turning to navigate - such as when you're hiking.
Also, when loading the pack, make sure the weight is evenly distributed on both sides. This is much more comfortable and much safer for your pup.
To give you an idea of just widely dog backpack designs can vary - which is a lot - I've included some of the styles offered on The Camping Dog Supplies website. As you look through these, notice how wide the variation is for saddle size, positioning on the body, materials, and purpose. These are arranged from the lightest possible pack through to the heaviest pack designed for serious hauling. Hopefully, looking at these will give you some good ideas and things to consider when you buy a pack for your dog.
Wenaha Light Rider This is a light duty pack designed to hold your keys, dog snacks and clean-up bags. This is a good example of one the simplest and most lightweight packs you can get. It's made with high quality materials and has reflective tape for high visibility. This is a type of pack you often find in pet stores, although this particular version is a better made. If you'd like to see more details about it, you can click on the picture to go to the details page of the website.
Kurgo Wander Pack
The Kurgo Wander Pack is an extremely well-made pack built strong to withstand rugged outdoor conditions yet functional for a day trip. Notice that the pack sits near your dog's shoulders, which is much safer for their spine. The saddles are smaller than you'll see in some of the following examples. Notice the way the pack straps on to the dog - paying attention to this kind of detail can help ensure you get a solid and safe pack when you're shopping.
The ergonomic padded spine support contours to the dogs back for a comfortable fit and provides weight distribution for the two saddlebags. The two saddlebags offer space to store travel essentials such as food, treats, toys, first-aid supplies and travel bowls. This particular pack, being smaller, isn't designed for carrying heavier items such as water bottles.
If you'd like to know more about this pack, click on the picture to go to the details page.
Wenaha Jogger Sport - Light Duty Pack This pack is a great example of a well-made pack that can carry larger, fairly light items such as water bottles. This is a light duty pack meant for "in-town" use. It has small panniers and an additional pocket on the front for a water bottle. The mesh pocket on the outside of the main bag allows easy access. This pack comes with a saddle which mounts on the dog and separate saddlebags attached with velcro fasteners.The under saddle works great as a tracking harness and has a loop to hook your leash.
Click on the picture if you'd like to see more details about it.
Wenaha Explorer 3 - Heavy Duty Pack
This is an example of pack designed for serious weight hauling. It comes with a saddle which mounts on the dog and separate saddlebags attached with velcro fasteners. It includes D-rings for extra tie-down capacity and compression straps to hold the pack securely through the roughest brush and rock. This dog backpack is made with 500 denier cordura on top and heavier ballistics material on the bottom for greater abrasion resistance. This is a mega-pack designed for a hard working dog.
As with the others, you can click on the picture to learn more.