Alex's quick reference guide

There are many useful guides online, but it can be difficult to get an accurate measurement without the tool that Osprey and Gregory hand out to retailers. I usually don’t bother because the length indication marks on the backpacks themselves don’t have numbers on them. To complicate things further, each manufacturer has its own sizing system that doesn't fully match up with others (at least they all have detailed instructions if you want to measure your exact torso length).

So what to do? Start here:

Osprey men’s packs run small in their small and medium sizes, and true-to-size in their large and extra-large sizes, when compared to their equivalent clothing size. Their women’s packs run small across the entire scale.

Gregory men’s packs run true-to-size compared to their equivalent clothing size. Their size markings are based on a single unisex scale (XS, S, M, and L), so there is no extra-small size for men, and no large size for women. Gregory packs have more generous sizing overall, but that means the smallest women may not be able to maintain tension on the hipbelt. If that's you, XS (or the combined XS-S sizing) will likely be the best option.

Deuter generally takes a one-size-fits-all approach with universal adjustment, the standard model being men’s fit, and model names appended with “SL” are women’s fit.

Fjällräven surprisingly does have marked length indicators in centimetres. “Small/Medium” is intended for women’s fit, and “Medium/Large” is intended for men’s fit. However, Small/Medium Fjallraven packs run large for smaller women, and if that's you, I recommend retracting the torso length to the minimum level.

Black Diamond runs small.

Most other manufacturers are wildly inconsistent. If you’re unsure, talk to the people at your local REI, MEC, or other outfitter to walk you through the fitting process.