How to Choose a Hiking Backpack Size (Liters and Fit)
Updated October 2026 · 3 min read
Quick answer
Choose 15–30 liters for day hikes, 30–50 liters for one or two nights, 50–70 liters for multi-day backpacking, and 70+ liters for long or winter trips. Then fit the pack to your torso length, not your height.
Backpack sizes are measured in liters of space, but the right pack is about two things: enough room for your trip, and a frame that fits your body. Get both right and even a heavy pack can feel comfortable.
Backpack size chart by trip
| Trip | Pack size | What it holds |
|---|---|---|
| Short day hike | 15–25 L | Water, snacks, rain jacket, Ten Essentials |
| Long or cold day hike | 25–35 L | Plus warm layers, more food and water |
| Overnight (1–2 nights) | 30–50 L | Light tent, sleeping bag, stove, food |
| Multi-day (3–5 nights) | 50–70 L | More food and fuel, extra clothes |
| Extended or winter trips | 70 L+ | Bulky winter gear, a week of food |
Measure your torso length
Pack frames come in sizes based on torso length, not your height. Two people of the same height can need different sizes.
- Tilt your head forward and find the bony bump at the base of your neck (the C7 vertebra).
- Put your hands on your hips with thumbs pointing back, on top of your hip bones (the iliac crest).
- Have a friend measure along your spine from C7 to the line between your thumbs.
| Torso length | Typical pack size |
|---|---|
| Up to about 17" (43 cm) | Small |
| About 17–19" (43–48 cm) | Medium |
| About 19" (48 cm) and up | Large |
Sizes vary by brand, so check the maker's chart. Many packs also have an adjustable back length.
How a pack should fit
- Hip belt first: center the padded belt on top of your hip bones and tighten it. On a loaded backpacking pack, most of the weight should sit on your hips, not your shoulders.
- Shoulder straps: snug them so they wrap your shoulders with no gaps — but don't let them carry all the weight.
- Load lifters: the small straps from the top of the shoulder straps to the pack. Pull them gently, to roughly a 45° angle.
- Sternum strap: clip it across your chest, about an inch below your collarbones.
Features worth looking for
- Padded hip belt — essential above about 15–20 pounds.
- Hydration sleeve for a water bladder. See hydration backpacks.
- Ventilated back panel — keeps your back cooler on hot hikes.
- Side and hip-belt pockets for snacks, phone, and water bottles you can reach without stopping.
- Rain cover — most packs are water-resistant, not waterproof.
- Women's-specific fit — shorter torso sizes and shaped straps and hip belts. See hiking backpacks for women.
How heavy should a pack be?
A common guideline for backpacking is to keep your loaded pack at or under about 20% of your body weight, and a day pack around 10%. Lighter packs (under about 3 pounds empty) save effort, but very light frames carry heavy loads less comfortably. See lightweight backpacks.
Where to start
- Day hikes: best daypacks
- All-around hiking: best hiking backpacks
- Multi-day trips: backpacks for long hikes
- On a budget: budget hiking backpacks
Not sure what goes in a daypack? See the day hike checklist.
Ready to buy?
Our recommended guides
Best Hiking BackpacksOur top packs for day hikes and overnights.
Our #1 pick: MOUNTAINTOP 40L Hiking Backpack
Best Packs for Long HikesBigger packs for multi-day trips.
Our #1 pick: TETON 65L Explorer Internal Frame Backpack
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Frequently asked questions
What size backpack do I need for a day hike?
15–25 liters for most day hikes, or 25–35 liters for long hikes, cold weather, or carrying extra gear for others.
Is a 40-liter backpack big enough for backpacking?
For one or two nights with compact, lightweight gear, yes. With bulkier gear or longer trips, a 50–65 liter pack is easier to pack.
How do I know my backpack size?
Measure your torso from the base of your neck (C7 vertebra) to the top of your hip bones, then match it to the maker's size chart. Height alone isn't a reliable guide.
Where should a hiking backpack sit?
The hip belt should sit centered on top of your hip bones, carrying most of the weight, with the shoulder straps snug but not bearing the full load.
Can I use a hiking backpack for travel?
Yes, many travelers use 35–45 liter hiking packs as carry-on bags. Check your airline's size limits, and look for a pack that opens like a suitcase for easier packing.