Hiking backpack sizes are given mainly in liters, which describe volume, not outside measurements. Physical dimensions vary a lot between models even at the same volume. This guide explains how to read both, what size suits which trip, and how to answer a few common sizing questions.
Liters vs. Physical Dimensions
A pack’s capacity in liters tells you how much it can hold. Its height, width and depth tell you how much space it takes up on your back, in a car trunk or in an airplane cabin. Two 30L packs can have noticeably different shapes: one tall and narrow, another short and wide. Check the manufacturer’s listed dimensions if the shape matters, for example for airline limits.
Some brands list capacity including exterior pockets and others do not, so volumes are approximate. Treat them as a guide.
Hiking Backpack Size Chart by Trip Type
These ranges are general guidance and not strict rules.
| Capacity | Typical use |
|---|---|
| Under 10 L | Trail running, very short walks, light carrying |
| 10 to 30 L | Day hikes |
| 30 to 50 L | Overnight trips and light weekend trips |
| 50 to 70 L | Multi-day backpacking in three-season conditions |
| 70 L and up | Winter, extended or expedition trips with bulky gear |
For a deeper look at how to choose among these, see our guide on what to look for in a hiking backpack.
What Size Is a 10L Backpack?
A 10L pack holds about ten liters of volume, which is a small bag. It usually fits a water bottle or small reservoir, a light jacket, snacks, keys and a phone. It is common for running, short walks or as a secondary pack. Its outside dimensions vary by brand, so check the product page for height and width. A 10L pack is generally too small for a full set of day hike essentials in cold or changeable weather.
Is a 50L Backpack Big Enough for Backpacking?
Often yes for short trips. A 50L pack is at the lower end of the typical multi-day range, and it can work for an overnight or a weekend, especially with compact, lightweight gear. If you carry a bulky sleeping bag, a large tent, winter clothing or several days of food, you may need more room. Pack your gear and see what fits before you decide. Our guide to what to pack can help you work out how much you will carry.
What Size Hiking Backpack Can You Carry On?
There is no single answer, because airlines set their own limits and they change. Carry-on bag limits are often given as overall dimensions in inches or centimeters, and many airlines also have a smaller limit for a personal item that fits under the seat. A small day pack of around 20 to 30L can fit within many carry-on limits, but a larger backpacking pack often does not, and its straps can snag on equipment if checked. Always check your airline’s current size rules, and measure the pack when it is filled, not empty.
Is 15.6 Inches Big for a Backpack?
That number usually refers to the largest laptop screen size a backpack’s padded sleeve can hold, not the size of the pack. A 15.6 inch laptop sleeve is common in daypacks and commuter bags. It does not tell you the pack’s volume, and many hiking packs list a hydration sleeve instead. If you plan to carry a laptop, look for the sleeve’s listed dimensions.
Torso Length Matters More Than Volume
A pack that holds the right amount but does not fit your back will be uncomfortable. Torso length, measured from the base of the neck (C7 vertebra) to the level of the top of the hip bones, is the measurement most brands use to assign small, medium or large. Many brands offer packs with adjustable back lengths. If you are between sizes, try both. Waist and hip size also affect the hip belt fit.
Other Things That Change the Size You Need
- Season: winter gear is bulkier.
- Gear weight and compressibility: down insulation and compact shelters save space.
- Trip length and food: food takes up a lot of room on longer trips.
- Group sharing: sharing a tent or stove cuts what you carry.
- Personal preference: some hikers like a snug pack; others prefer spare room.
Test the Size Before You Commit
Load the pack with your real gear or with equivalent weight, wear it for a while, and check that it sits well. If a pack feels too large, compression straps can help. If you find yourself strapping lots of items to the outside, you probably need more capacity.