The size of the backpacks depends on the child's age. A good school backpack should be no larger than the child's back. You can take two measurements of a child's back and use those for the maximum height and width of the backpack. Here is the steps.
Height size of the school backpack
Find the maximum height by measuring the distance from the shoulder line to the waistline and adding 2 inches. The shoulder line is where the backpack straps will actually rest on the body. This is located about halfway between the neck and shoulder joint. The waistline is at the belly button. The backpack should fit 2 inches below the shoulders and up to 4 inches below the waist, so adding 2 inches to the measurement will give the right number.
Width size of the school backpack
The width of the back can be measured at a number of locations, each with different results. For a backpack, the core and hip muscles usually carry the most weight. This is why the backpack should be kept centered between the shoulder blades. To find the proper width for a backpack, measure between the ridges of your kid's shoulder blades. Adding an extra inch or 2 here is acceptable.
Size Chart for Children's Backpacks
If you cannot measure your child for whatever reasons, like if they refuse to sit still or if you cannot find any measuring tools, that means you have to guess. This chart can help ensure that a guess is as accurate as possible. The chart shows the maximum heights and widths for the average child of a certain age. Make adjustments as necessary.
Of course, you can also choose a backpack of the right size for your child in the following ways.
Since your elementary school-aged child will most likely just be hauling around some colored pencils, a few folders, and a notepad or two, they won’t be needing an oversized backpack . Recommended size： 18.6″ H x 13.8″ W x 6.5″ .
Your child has reached the grade level where they have to start lugging around those heavy textbooks, and they are going to need a sturdy and comfy backpack to give them a helping hand. Slightly larger than the previous backpack. So the recommended school backpack size is 27 liters .This is enough space to carry enough items for your child without appearing too heavy.
High School and College
It’s a tad more tricky picking the right backpack for your child that’s no longer a child, and you also have to think about the “cool factor”. Fashion looks, the right size, and the right function are all things to consider when choosing a backpack . All you have to do is give some advice, and the final decision is up to your big boy.