Determine backpack size yourself

How to find the perfect fit

For the perfect fit of your dog backpack, all measurements are important. Here you will learn how to measure your dog’s shoulder height, back length, seat/lying width, and weight yourself to find the right size.

Find the perfect size for your backpack by determining your dog’s key measurements.

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1. Measure the dog

To find the perfect fit, your dog’s back length and shoulder height are the most important measurements. It’s best to measure your dog while they are standing.

  • Back length is measured from the withers to the base of the tail (where the tail begins).
  • Shoulder height is measured from the ground to the highest point of the shoulder blade along the front leg.
Illustration showing how to measure a dog for a backpack, with marked back length, neck circumference, chest circumference, and shoulder height.
Illustration of a dog sitting in a backpack, with measurements for the backpack size and the dog.
Illustration of a dog backpack and a seated dog next to it, showing the proportional sizes.

2. Note shoulder height & weight

In addition to the space your dog needs to sit or lie down, shoulder height and weight are important factors when choosing the right backpack.

  • Your dog’s shoulder height should be no more than 2 cm below the top edge of the window, so they can look out comfortably without bumping their head.
  • Weight provides a basic guideline for the backpack’s load capacity. It’s an important reference but should never be the only factor in your decision.

Not sure about the size? Try our sizing quiz.

Illustration of a standing dog in a backpack, showing that the shoulder height should be within the window area.
Illustration of a dog sitting in a backpack, showing that the shoulder height should be in the area of the window.

3. Determine reclining width (optional)

Lying width is important if your dog should be able to lie down comfortably inside the backpack.

  • How to measure: Measure your dog while they’re lying down relaxed with paws tucked in – from the widest point of the body to the base of the tail.
  • Important: Inside the backpack, your dog will naturally curl up a bit for stability, so they won’t lie completely stretched out. A backpack that’s too wide can become unwieldy and less stable.
  • Rule of thumb: The backpack width should roughly match your dog’s back length. If you want a bit more space, you can add up to 5 cm (2 in).
  • Exception: In the MountainRock Backpack and ROOFPACKER, dogs usually curl up more while lying down.
  • Recommendation: For dogs that like to lie down and look out, we recommend the PeakStone, Dachshund, Bulldog Backpack, or ROOFPACKER.
Illustration of a dog lying in a backpack, showing that the length of the dog's back should correspond to the width of the backpack.

4. The right-angled triangle: The ultimate tip for dogs that sit

Seat width is crucial when your dog is supposed to sit comfortably in the backpack.

  • Calculation (using the size calculator):
    • Enter your dog’s back length and shoulder height into our calculator.
    • Rule of thumb: Add about 10 cm to the calculated seat width. This value should be less than or equal to the backpack’s width.
    • Applies to: PeakStone, Dachshund, and Bulldog models. For the MountainRock Backpack and ROOFPACKER, the space can be smaller.
  • Direct measurement (using a measuring tape):
    • Rule of thumb: When measuring seat width directly, the backpack should be about 3 cm wider to ensure your dog can sit comfortably.
    • Applies to: PeakStone, Dachshund, and Bulldog models. For the MountainRock Backpack and ROOFPACKER, dogs can also sit slightly turned inside.
Illustration showing how to calculate the seat width for a dog in a backpack using the Pythagorean theorem and adding 10 cm.

Calculate Seat Width

Enter your dog's shoulder height and back length.

5. Important Tips for the Perfect Fit

Here are the key rules to help you check the fit:

  • Sitting vs. Lying Position: Keep in mind that your dog won’t always stay in the same position inside the backpack as they do on the ground. They’ll often curl up a bit or tuck in their paws.
  • Individual Needs: Every dog’s proportions and every human’s body shape are different. That’s why we recommend reviewing the results based on your personal needs. This is the best way to ensure that your dog feels comfortable in the backpack and that it works well for you, too.
Illustration of a dog sitting upright in a backpack and looking out.
Illustration of a dog lying down in a backpack.
Illustration of a dog lying relaxed in a backpack.
Illustration of a dog sitting in a different style of backpack.

6. Example: PeakStone Backpack

It’s important to consider all measurements to find the right backpack size for your dog.

Illustration of a square dog that fits perfectly in a PeakStone Backpack rucksack to illustrate the correct fit.

Example A: A square-shaped dog (shoulder height and back length are the same) fits in the backpack.

Illustration of a dog with shoulder height too high in the backpack, showing that the dog does not fit inside.

Example B:
 A dog with shoulders that are too tall (not at least 2 cm below the window) does not fit in the backpack.

Solution:
 Choose a larger size of the PeakStone Backpack – in this case, size Large.

Illustration of a short but very long dog that does not fit into the backpack.

Example C:
 A short (low shoulder height) but very long dog does not fit in the backpack.

Solution:
 Choose a different backpack model that suits your dog’s body shape. In this case, the Dachshund Backpack.

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