Your height does not tell a backpack maker where your shoulders sit relative to your hips. Two travelers of the same height can need different harness lengths. A torso measurement gives you a more relevant starting point, especially when choosing a travel pack with an adjustable harness.
What you need to measure
Use a flexible tape and ask another person to help if possible. Trying to read a tape behind your own back encourages you to bend and shifts the position you are measuring. Wear a light layer that lets your helper locate the landmarks without guessing through a bulky coat.
Osprey's instructions measure from the prominent C7 point at the base of the neck to the level of the iliac crest, the top of the hip bones. Its sizing page includes a diagram. Follow the manufacturer's illustrated method rather than measuring from the top of your head or using your trouser inseam.
Record a measurement you can repeat
Locate both landmarks first. Stand naturally while your helper follows the route shown in the guide, then record the result and unit. Repeat the process from the beginning instead of leaving the tape in place and reading it twice. A noticeable difference between attempts usually warrants another careful measurement.
Keep inches and centimeters clearly labelled. If a size chart uses different units, convert once and retain the original measurement beside it. Rounding too early can push a value across a listed size boundary. You do not gain useful precision by recording several decimal places from an uncertain tape position.
Use the chart for that exact backpack
Find the current product's torso or harness chart. A general brand chart may cover hiking, everyday and travel packs with very different ranges. A designation such as small/medium is meaningful only within the model's own sizing information. Liters describe capacity, not the length of the person the harness fits.
For example, imagine a measured torso falling inside two overlapping size ranges. That overlap gives you two candidates to try; it does not prove they will feel identical. Hipbelt coverage, shoulder spacing and how the pack sits when loaded still matter. Treat this as a hypothetical sizing example, not a size recommendation.
What to do when no torso range is published
Ask the maker whether the harness is fixed and what fit guidance it provides. Do not replace missing information with the bag's external height. Exterior dimensions help with luggage restrictions, but they do not reveal where the shoulder straps attach or where a supportive belt is intended to sit.
If you can try the bag with your usual load, use your measurement to keep the comparison organized rather than to overrule your experience. A plausible chart match is a reason to test the fit. A poor loaded fit remains poor even when the numbers appear compatible.
Keep your torso measurement, the model's stated range and the setting that worked in one note. Add a photo of the adjustment position if the harness uses several attachment slots. That record makes future shopping easier and helps you restore the setup after another person borrows the pack.
