Quick answer: choose a backpacking pack by trip length, fit and the weight you will carry. Outfitter guidance such as REI’s suggests roughly 30 to 50 liters for an overnight or weekend trip, 50 to 80 liters for three to five nights, and 70 liters or more for longer or winter trips. Fit matters more than brand: measure your torso length from the bony bump at the base of your neck (the C7 vertebra) to the top of your hip bones (the iliac crest), and pick a pack and hip belt sized for those measurements. A well-fitted hip belt should carry most of the load on your hips, not your shoulders.
Your backpack is the piece of gear you feel every single step of a trip. Sure, a tent that is a little heavy or a stove that is a little slow is a minor annoyance, but a pack that does not fit can turn a beautiful trail into hours of sore shoulders and bruised hips. The good news is that choosing a pack follows a clear order: decide on volume, get your measurements, then compare frames and features.
This guide walks through each step. It is part of our camping checklist guide, which covers the full gear list for car camping and backpacking.
Sources: REI Expert Advice articles on choosing backpacks and measuring torso length; manufacturer fit guides from major pack makers; National Park Service backcountry trip planning pages; Leave No Trace Center for Outdoor Ethics. Capacity ranges are general guidance, not fixed rules. Checked October 2026.
Step 1: Decide How Much Capacity You Need
Pack volume is measured in liters. The right size depends on how many nights you will be out, how bulky your gear is and the season.
| Trip length | Typical capacity | Notes |
|---|---|---|
| Day hike | 15 to 30 liters | Water, layers, food, first aid |
| Overnight to weekend (1 to 3 nights) | 30 to 50 liters | Works best with compact, lighter gear |
| Multiday (3 to 5 nights) | 50 to 80 liters | Most popular range for backpackers |
| Extended trips (5+ nights) | 70 liters or more | More food, sometimes a bear canister |
| Winter trips | 70 liters or more | Bulkier sleeping bag, extra layers |
These ranges reflect outfitter guidance such as REI’s and are a starting point. Someone with a small down sleeping bag and a lightweight tent can fit a weekend into 40 liters, while someone with older, bulkier gear may need 60 liters for the same trip.
Questions that change the answer
- Do you need a bear canister? Many parks, including several in the Sierra Nevada, require hard-sided food containers in some areas. Canisters take up a lot of space inside the pack.
- Will you carry gear for others? Parents carrying a child’s sleeping bag and food need extra room.
- How compressible is your sleeping bag? Synthetic bags pack larger than down bags with the same rating. Our guide to choosing a sleeping bag and pad explains the trade-offs.
- How much water must you carry? Dry routes in the desert require more capacity for bottles or reservoirs.
A common mistake is buying a huge pack “just in case.” Extra space tends to get filled with things you do not need, and a bigger pack usually weighs more empty.
Step 2: Measure Your Torso and Hips
Pack sizes are based on torso length, not height. Two people of the same height can need different sizes.
How to measure torso length
- Find your C7 vertebra. Tilt your head forward; the bony bump at the base of your neck is C7.
- Find your iliac crest. Place your hands on your hips with thumbs pointing backward. The top of your hip bones is the iliac crest.
- Measure between them. Have a friend run a flexible tape measure along your spine from C7 to the imaginary line between your thumbs.
REI and many pack makers describe this same method. Manufacturers then publish torso ranges for each size, such as small, medium and large, and many packs have adjustable harnesses to fine-tune the fit.
Hip belt size
Wrap a tape around your hips at the iliac crest, where the hip belt will sit. This is usually a little higher than your pant waist. Many packs offer interchangeable hip belts in different sizes, which helps if your torso and hips fall into different size categories.
Women’s and gender-specific packs
Packs marketed for women typically have shorter torso ranges, narrower shoulder straps shaped to sit around the chest, and hip belts angled for a different hip shape. Many people of any gender find one style or the other fits better. Try both if you can.
Step 3: Choose a Frame Type
| Frame type | How it works | Pros | Cons |
|---|---|---|---|
| Internal frame | Stays or a frame sheet inside the pack | Stable, close to the body, most common | Back can get sweaty |
| External frame | Visible frame outside the pack bag | Carries heavy, awkward loads; good ventilation | Bulkier, less stable on rough terrain |
| Frameless | No rigid frame; often uses a sleeping pad for structure | Very light | Comfortable only with light loads |
Most backpackers today use internal-frame packs because they hug the body and move well on uneven trails. External frames are still popular with some hunters and trail crews who carry heavy, oddly shaped loads. Frameless packs suit ultralight hikers whose total load is low.
Ventilated back panels
Some packs use a suspended mesh back panel that holds the pack away from your back for airflow. These can be cooler in hot weather, but they shift the center of gravity slightly back from your body.
Step 4: Compare Key Features
Not every feature matters to every hiker. These are the ones that tend to make a difference.
Suspension and hip belt
The suspension system includes the shoulder straps, hip belt, load lifters and sternum strap. Look for a hip belt with firm padding that wraps over your hip bones. REI’s fitting guidance describes the hip belt as the part of the pack that should carry most of the weight.
Access points
- Top loading is the traditional design and is the lightest and strongest.
- Front panel or U-zip access lets you reach gear in the middle of the pack without unloading.
- Bottom zippered compartments are handy for a sleeping bag.
Pockets and storage
- Hip belt pockets for snacks, a phone or sunscreen
- Side water bottle pockets you can reach while walking
- A stretch front pocket for a rain jacket or wet layers
- A lid or brain for small items
Hydration compatibility
Many packs have a sleeve and a port for a hydration reservoir. Others are designed around bottles. Choose the system you will actually use.
Weight
Empty pack weights range from under 2 pounds for minimalist designs to more than 5 pounds for heavily featured packs. Lighter packs often have less padding and a lower recommended maximum load. Check the manufacturer’s suggested load range and stay within it.
Rain protection
Most pack fabrics are water resistant but not waterproof, and seams leak in steady rain. Many hikers use a pack liner or dry bags inside the pack, a rain cover outside, or both.
Step 5: Try It On With Weight
Fit is hard to judge with an empty pack. Many outdoor stores have weighted bags for this purpose, or you can load the pack with your own gear at home. Here is the order REI and most pack makers describe:
- Loosen all the straps.
- Put the pack on and position the hip belt so it sits over your iliac crest, then tighten it snugly.
- Tighten the shoulder straps until they wrap your shoulders without gaps, but do not pull the weight off your hips.
- Adjust the load lifters, the small straps between the top of the shoulder straps and the pack. They are often set at around a 45-degree angle.
- Clip and adjust the sternum strap so the shoulder straps sit comfortably across your chest.
- Walk around, climb stairs and lean to see how the pack moves.
If the shoulder straps connect well below your shoulders or above them, the torso size or harness setting is wrong.
Can One Pack Do Everything?
Many new backpackers hope to buy a single pack for day hikes, weekends and week-long trips. It can work, but it involves compromises. A 50- to 60-liter pack with good compression straps is often the most versatile size, because you can cinch it down for shorter trips and still fit a few nights of gear. Removable lids and hip belt pockets help reduce weight when you do not need them.
For day hikes, though, a large backpacking pack is usually heavier and warmer than necessary. A separate 20- to 30-liter daypack is inexpensive compared with a backpacking pack and gets used far more often. Some backpacking packs include a detachable lid that converts into a small hip pack or summit bag, which can cover short side trips from camp.
If you plan to take one big trip a year, renting a pack from an outdoor retailer or university outdoor program is another option. Renting lets you test sizes and styles before you buy, and it is a good way to learn which features you actually use.
Whatever you choose, take the pack on at least one shorter loaded hike before a big trip. Small fit issues, like a hip belt that rubs or a shoulder strap that pinches, show up after a few miles, not in a parking lot.
How to Load a Backpacking Pack
Even the best pack carries poorly when it is loaded badly. A common approach looks like this:
- Bottom: bulky items you will not need until camp, such as your sleeping bag and sleep clothes
- Middle, close to your back: the heaviest items, such as food, the cooking kit, water and a bear canister
- Top: items you may need during the day, such as an insulating layer, water filter and toilet kit
- Outer pockets and lid: map, snacks, sunscreen, headlamp, first aid kit and rain gear
Keeping heavy items centered and close to your spine improves balance. Our article on backpacking food planning explains how to keep food weight down.
How Much Weight Should You Carry?
There is no single correct weight, but lighter loads are easier on knees, hips and feet. Many outfitters suggest that a loaded backpacking pack should stay around 20 percent of body weight or less for most people, and lighter is more comfortable. Ways to cut weight include sharing tents and cooking kits within a group, repackaging food, and leaving duplicate items at home.
New vs Used Packs
Used packs can be a good value, but check them carefully. Look for torn mesh, frayed straps, broken buckles, delaminating coatings and damaged frame stays, and make sure the size matches your torso measurement. Our guide to buying used camping gear has a full checklist.
Caring for Your Pack
- Empty it after every trip and shake out crumbs and dirt.
- Hand wash with mild soap when needed; avoid washing machines unless the maker allows it.
- Air dry fully out of direct sun before storage.
- Store it loosely in a cool, dry place.
Our guide to camping gear care covers cleaning and storage for the rest of your kit.
Common Mistakes When Choosing a Backpack
- Buying by height or by clothing size instead of torso length.
- Choosing the largest pack available, which tends to encourage overpacking.
- Testing the pack empty in the store.
- Wearing the hip belt too low, on the waist rather than over the hip bones.
- Letting the shoulder straps carry the load. Most of the weight should sit on your hips.
- Ignoring returns policies. A short test hike at home with full weight can reveal problems early.
Frequently Asked Questions
What size backpack do I need for a 3-day backpacking trip?
Outfitter guidance generally suggests about 30 to 50 liters for a two- to three-night trip with compact gear, and up to 60 liters with bulkier gear or a bear canister.
How do I measure my torso for a backpack?
Measure along your spine from the C7 vertebra at the base of your neck down to the top of your hip bones, the iliac crest. Compare that number to the manufacturer’s size chart.
Where should the hip belt sit?
The hip belt should sit over your iliac crest, the top of your hip bones, so it can carry most of the load.
Is an internal or external frame pack better?
Internal-frame packs are more stable and are the most common choice for trails. External frames carry heavy or awkward loads well and allow more airflow.
How heavy should my loaded backpack be?
Many outfitters suggest keeping a loaded pack around 20 percent of body weight or less. Lighter loads are generally more comfortable.
Are backpacking packs waterproof?
Usually not. Most are water resistant, so use a pack liner, dry bags or a rain cover in wet weather.
