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Backpack torso length is the measurement used to match the pack’s harness to your back. It is different from your overall height. Two people who wear the same trouser size or stand equally tall can need different rucksack sizes.
Table of Contents
Find the measurement points
Use the fitting method specified by the backpack manufacturer. In Osprey’s torso-measuring guide, the measurement runs from the prominent C7 vertebra at the base of the neck to the level of the iliac crest, the top of the hip bones. Ask another person to help with a flexible tape rather than twisting to read it yourself.
Measure more than once and record the result in centimetres. A rushed measurement can put you on the wrong side of a size boundary. If you cannot confidently locate the landmarks, a specialist shop fitting is more useful than repeatedly guessing.
Read the chart for the actual model
A label such as small/medium is not universal across brands or even across every backpack in one range. Find the size chart for the exact model and generation. Some packs have an adjustable harness within a stated range; others have a fixed back length. An adjustable sternum strap alone does not mean the torso length adjusts.
If you fall between sizes, try both where possible. Compare the shoulder strap shape and hipbelt position under load. Do not automatically size up because you intend to carry more equipment: capacity and body fit are different measurements.
Turn the measurement into a loaded fitting
Start with the manufacturer’s adjustment sequence. Loosen the straps before putting the pack on, position the hipbelt as directed, then make small adjustments. Use a representative load, with hard items packed so that they do not press into your back.
- Check whether the shoulder straps follow your shoulders without an obvious gap.
- Check that the belt stays in its intended position as you walk.
- Reach forward and look up; the pack should not force an awkward posture.
- Notice whether you keep tightening one strap to compensate for another problem.
Pressure, slipping or restricted movement are reasons to reassess the fit. They are not problems to dismiss because a measurement falls within the printed range.
A product example to inspect
The Osprey Hikelite 26 Atlas Blue S/M listing on Amazon UK illustrates why the full variant matters. The size designation belongs to that listing; do not transfer it to every Hikelite 26 sold under the same family name. Check the corresponding manufacturer’s documentation before choosing.
Keep a useful fitting record
Record your torso measurement, the pack model, the size tried and what happened when it was loaded. A note such as “belt slipped while walking” is more useful than “medium felt wrong”. If an adjustable pack works well, record the harness setting too.
Recheck the setup when you lend the rucksack to someone else or substantially change its load. Correct measurement narrows the choice, but a comfortable real-world fit remains the final test.
Use our hipbelt fitting guide for the next stage of the loaded trial. Our daypack sizing guide helps decide whether the job needs a small day bag or a larger camping rucksack.
Continue with our rucksack buying guide.
Reviewed 10 September 2026. This guide is based on published specifications and guidance.