Method and limits

Measure the loaded backpack on the child with both straps adjusted. Enter the vertical shoulder-line-to-waist span, how far its top sits below the shoulder line and its outside height. The tool subtracts the span from the top gap plus bag height. The American Academy of Pediatrics says the bag should extend from the waist to about 1–2 inches below the shoulders, never more than 4 inches below the waistline.

For load, divide the fully packed bag weight by the child’s body weight. AAP and the Pediatric Orthopaedic Society of North America recommend a full bag at or below 15% of body weight. This is a ceiling for this worksheet, not a guarantee that a child will be comfortable or injury-free.

For a required school item, the tool compares its measured width and height with the usable inside bag width and height, including a 90° rotation. A 2D fit does not account for depth, seams, zippers or packed contents. If a value is missing, its check stays unknown. Any failed check means remeasure or change the bag. This worksheet never diagnoses pain, approves a medical or safety condition, or replaces school-specific requirements. For pain, numbness, surgery or injury, consult a pediatrician. Sources checked 2 October 2026.