How to Choose the Right Ultralight Backpack for Your Torso Length

Quick Answer

To choose the right ultralight backpack, first measure your torso length from the C7 vertebra to your iliac crest. Then match that measurement to the pack's size range, and verify the hip belt sits on your hip bones. For Zpacks, models like the Sub-Nero Ultra 30L are designed for a range of torso lengths, but always check the specific sizing chart.

A well-fitting backpack is the foundation of a comfortable hike. When a pack is too long or too short, you'll feel it in your shoulders, hips, and back. For ultralight gear, fit is even more critical because frameless packs rely on your body to provide structure. This guide explains how to measure your torso and match it to a pack.

We'll walk through the steps of measuring, what to look for in a pack's fit, and how to test a pack before you buy. You'll also learn why hip belt placement and shoulder strap angle matter just as much as torso length.

Why Torso Length Matters for Ultralight Backpacks

Torso length determines where the shoulder straps sit and how the pack transfers weight to your hips. If the pack is too long, the hip belt will sit too low, forcing the shoulder straps to carry weight that should go to your hips. If it's too short, the hip belt will press on your ribs, and the shoulder straps may dig into your neck.

Ultralight packs often have minimal padding and no heavy frame, so a precise fit is essential. The right torso length ensures the load rides on your hip bones, keeping your shoulders free and your posture natural.

• Always measure your torso length, not your overall height, when choosing a pack.

How to Measure Your Torso Length

You'll need a flexible measuring tape and a friend to help. First, tilt your head forward and feel for the prominent bone at the base of your neck—that's the C7 vertebra. Place one hand on that spot. Then, place your other hand on your hip, finding the top of your iliac crest (the bony ridge). Have your friend measure the distance between your hands.

This measurement in inches or centimeters is your torso length. For example, a torso length of 16-19 inches typically corresponds to a small/medium pack, while 19-21 inches is medium/large. Always refer to the manufacturer's sizing chart, as sizes vary between brands.

• If you're between sizes, consider the load you'll carry and the pack's adjustability.

Matching Your Measurement to a Zpacks Backpack

Zpacks offers several backpacks with different sizing options. For instance, the Sub-Nero Ultra 30L Backpack is a frameless pack that comes in multiple torso sizes. It features interchangeable shoulder straps and a removable belt, allowing you to fine-tune the fit. When choosing a size, consider your torso length and the type of trips you'll take.

If you're between sizes, think about your layering system. A thicker jacket might require a slightly larger size to maintain comfort. Also, remember that a frameless pack's fit can change when it's loaded, so you want a snug but not tight fit when empty.

• Check the product page for a detailed sizing chart before ordering.

Testing the Fit: Hip Belt and Shoulder Straps

Once you have a pack on, loosen all straps, then tighten the hip belt first. The belt should sit on your hip bones, not your waist. After securing the hip belt, adjust the shoulder straps so they follow the contour of your shoulders without gaping. The load lifter straps (if present) should angle at about 45 degrees.

Walk around with the pack loaded as it would be on the trail. Check for any pressure points or movement. The pack should feel stable, and you should be able to move your arms freely. If the pack pulls on your shoulders or shifts side to side, the fit isn't right.

• A properly fitted pack allows you to loosen the shoulder straps slightly without the hip belt slipping.

Decision Rules for Choosing Your Ultralight Backpack

• Measure first: Always measure your torso length before comparing packs. Use the C7-to-iliac-crest method and record the number. Your torso length is the primary filter for pack size.
• Check the hip belt: The hip belt should sit on your hip bones, not your waist. If it doesn't, the torso length is wrong. A proper hip belt fit transfers weight to your hips and reduces shoulder strain.
• Consider adjustability: Packs with interchangeable straps or adjustable torso lengths offer more flexibility, especially if you're between sizes or plan to use the pack for different activities. Adjustable features can extend the life of your pack as your body or gear changes.

Zpacks Backpacks and Fit

• Sub-Nero Ultra 30L Backpack (DISC): The Sub-Nero Ultra is a smaller and slightly more stripped down version of our popular Nero Ultra Backpack. Streamlined to only the most essential features, the Sub-Nero Ultra is great for hikers with dialed in base weights and minimalist kits. With 3 different interchangeable strap designs, a removable belt, and a... This pack's adjustable features let you fine-tune the fit to your torso length and hip size, making it a versatile choice for ultralight hikers.
• Backpacks: Zpacks backpacks are designed for hikers and adventurers who value lightweight, dependable gear on the trail. This collection offers a range of packs built to help you carry your essentials comfortably and efficiently. Part of the Zpacks lineup, known for durable, ultralight backpacking equipment. Available in a Standard configuration to suit a variety of outdoor trips. Engineered with a focus on reducing pack weight... The Zpacks backpack lineup includes various models with different sizing and features, so you can find one that matches your torso length and trip needs.

Fit Guidance

Best for

• Hikers with a measured torso length that falls within the pack's size range and who prioritize a lightweight, minimal design.
• Ultralight enthusiasts who prefer a frameless pack and are comfortable with a dialed-in base weight.

Not for

• Hikers who need a heavy-duty frame to carry loads over 25 pounds.
• Those who are between torso sizes and prefer a pack with extensive adjustability over a fixed size.

Choosing the right ultralight backpack starts with an accurate torso measurement and a clear understanding of how fit affects comfort. By following the steps above and considering the adjustability of models like the Sub-Nero Ultra, you'll find a pack that carries well and keeps your adventures light.