Torso length

Torso length is the distance measured along your back from the bony bump at the base of your neck down to the level of your hip bones, and it is the key measurement backpack manufacturers use to size a bag's frame and shoulder strap position. It is a different measurement from a person's overall height, so two people of the same height can need different backpack sizes if their torso proportions differ.

Fitting a bag to torso length matters because a frame that is too long or too short changes where the weight sits, which can push weight onto the shoulders instead of the hips, or cause a hip belt to sit too high or low to do its job. This matters more for larger or heavier backpacks than for very small daypacks, where fit tolerance is looser.

To check fit, most brands publish a torso length range for each bag size, and some backpacks come in adjustable or multiple frame sizes to fit a wider range of people. A common mistake is choosing a bag size based on overall height alone, or based on what size a friend uses, without measuring torso length directly, which can lead to a bag that never quite sits right no matter how the straps are adjusted.