Backpack Sizing and Fit Guide: How to Load Test Before You Hit the Trail

Why Fit Matters More Than Features

A $400 pack with the wrong torso length feels worse than a $150 pack that fits. REI's data from 200,000+ fittings annually shows 60% of customers come in wearing the wrong size.

How to Measure Torso Length

1. Find your C7 vertebra (bony bump at base of neck when you tilt head forward)
2. Find your iliac crest (hands on hips, thumbs pointing back — where thumbs meet spine)
3. Measure the distance along your spine. That's your torso length.

80/20 Rule of Load Distribution

A properly fitted pack puts 80% weight on hips, 20% on shoulders. If shoulders bear most weight: wrong fit, wrong hip belt position, or unadjusted load lifters.

Top Picks

Osprey Atmos AG 65

$290 Check Price on Amazon

Anti-Gravity suspension. 65L for 3-5 day trips. Backpacker Magazine Editors' Choice 3 years running. 4 lbs 8 oz.

Gregory Baltoro 75

$330 Check Price on Amazon

Response A3 suspension, rain cover included. 75L for extended trips. Most adjustable sizing in the industry. 4 lbs 14 oz.

How to Load Test In-Store

1. Load pack to expected trail weight using store sandbags
2. Walk 15+ minutes. Use stairs if available.
3. Check: 80% weight on hips? Can look up without lid hitting head? Shoulder straps wrapping without gaps?
4. Adjust load lifters to 25-45 degrees

Sources

1. REI Expert Advice. "How to Fit a Backpack." rei.com, 2025.
2. Osprey Pack Fitting Guide. osprey.com, 2025.
3. Backpacker Magazine. "Pack Test 2024."