Backpack Size & Torso Fit Calculator

Measuring your torso

Torso length runs from the bony bump at the base of your neck (the C7 vertebra — tilt your head forward to find it) down to the imaginary line between the tops of your hip bones (iliac crest). Have a friend measure along your spine with a soft tape while you stand straight. Most adults fall between 15 and 22 inches. Our step-by-step torso guide covers it in detail.

Typical size ranges

Ranges overlap and differ between brands, which is why many packs have adjustable harnesses. Capacity matters as much as fit: a bigger pack tempts you to carry more. For most people with modern gear, 40–55 liters covers weekend trips. Want to rent before you commit? See where to rent camping gear.

Frequently asked questions

What size backpack do I need for a 3 day hike?

For a 2 to 3 night backpacking trip, most people need 40 to 55 liters with typical modern gear, or 35 to 45 liters with ultralight gear.

Is backpack size based on height?

No. Backpacks are sized by torso length, from the C7 vertebra at the base of your neck to the top of your hip bones. Two people of the same height can need different sizes.

What size daypack do I need?

18 to 30 liters fits water, layers, food, and the Ten Essentials for a full day hike. Go toward 30 liters for winter or if you carry gear for kids.