Hiking backpacks are measured in liters of capacity, and the right size depends on the length of your trip: roughly 10 to 30 liters for day hikes, 30 to 50 for overnight trips, and 50 or more for multi-day backpacking. Choosing the right size matters because a pack too small will not hold your gear while one too large tempts you to overpack and carry needless weight. Matching the capacity to how you actually hike is the whole point of a size guide.
Backpack Sizes by Trip Length
| Trip type | Rough capacity | What it holds |
|---|---|---|
| Short day hike | 10 to 20 liters | Water, snacks, essentials |
| Full day hike | 20 to 30 liters | Above plus layers, more water, extras |
| Overnight trip | 30 to 50 liters | Sleep and camp gear for one night |
| Multi-day backpacking | 50 liters and up | Multiple days of food, shelter, gear |
What Liters Actually Mean
The liter rating of a backpack is its total carrying volume, the amount of space inside for your gear. A higher number means more room, so a 20-liter pack holds a day’s essentials while a 60-liter pack swallows days of camping gear. Because it measures volume rather than weight, the liter figure tells you how much stuff fits, not how heavy it will be, though naturally a bigger pack filled up carries more weight. Understanding that liters equal space is the foundation for picking the right size, since you are matching the space to the gear you need to bring. Hiking daypacks cover the smaller end of the range.
Day Hike Sizes
For day hikes, a pack in roughly the 10 to 30 liter range covers most needs. At the smaller end, 10 to 20 liters holds the essentials for a shorter outing: water, snacks, and a few items. Toward 20 to 30 liters, you get room for more water, extra layers, a fuller lunch, and any additional gear a longer or more varied day hike calls for. Most day hikers are well served somewhere in this band, and choosing within it comes down to how much you tend to carry and how long your typical hikes run. A daypack is about carrying a day’s essentials comfortably, not hauling camp gear. Hiking backpack vs daypack covers the distinction.
Overnight and Multi-Day Sizes
Once you are sleeping outside, capacity needs jump. An overnight trip, one night out, generally calls for something in the 30 to 50 liter range to fit sleeping gear, shelter, food, and the extra clothing an overnight requires. For multi-day backpacking, 50 liters and up becomes necessary to carry several days of food along with shelter and sleep systems, with longer or more involved trips pushing the capacity higher. These larger packs also add features like hip belts and frames to carry heavier loads comfortably, since the weight climbs with the capacity. Matching the size to the number of nights is the key at this end. Backpacking tents cover the shelter that drives some of this volume.
Why Bigger Is Not Better
It is tempting to buy a large pack to be safe, but oversizing has a real downside: a big pack invites you to fill it, and a fuller pack means more weight on your back for gear you may not need. Carrying a half-empty oversized pack also lets the load shift around, which affects comfort and stability. The better approach is to size the pack to your actual needs so it is comfortably full rather than either bursting or swimming with empty space. Buying more capacity than your hiking calls for usually just means carrying a heavier, bulkier pack than necessary. Right-sizing keeps you comfortable and honest about what you actually need to carry on the trail. Packing a hiking backpack covers loading whatever size you choose.
How Your Gear Affects the Number
Within any trip-length range, the exact size you need depends on how bulky your gear is and how you pack. Two day hikers can both need a daypack while landing at different liters, one at 15 because they carry water and snacks and little else, another at 28 because they bring layers, a bigger lunch, camera gear, or extra water for a long desert hike. The trip length sets the range; your personal kit sets where you fall in it. Bulky items like a puffy jacket or extra water eat volume fast, so if you tend to carry more, size toward the upper end of your range rather than the bottom. Packing light lets you go smaller and lighter, which is more comfortable to carry. Thinking about the gear you actually bring, not just the trip type, is what lands you on the right number. What to pack in a daypack covers a typical day-hike load.
Choosing Your Size
To pick a size, start with the kind of hiking you actually do most. If you are a day hiker, a pack in the 10 to 30 liter range matched to how much you carry is right, leaning smaller if you pack light and larger if you bring more. If you head out overnight, move into the 30 to 50 liter range, and for multi-day trips, 50 liters and up. Consider your typical trip rather than the occasional exception, since it is usually better to size for your normal hiking and adapt for rare bigger trips than to lug a huge pack for everyday outings. The right size is the one that fits your real hiking life rather than an occasional exception. Hiking daypacks cover choosing at the day-hike end.
Recommended Reading
Worth reading next: hiking daypacks, hiking backpack vs daypack, packing a hiking backpack, and hiking backpacks under 100.
The Bottom Line
Choosing a backpack size is about matching liters to how you actually hike. Day hikes live in the 10 to 30 liter range, overnight trips in the 30 to 50 range, and multi-day backpacking at 50 liters and up, with your gear volume and packing style setting the exact number within each band. The temptation to size up for safety usually backfires, since a bigger pack invites overpacking and a heavier load, while a half-empty oversized pack shifts around and hurts comfort. Size for your normal hiking rather than the rare exception, so the pack rides comfortably full, and handle occasional bigger trips separately. The right size is the one that fits your real hiking life, not the largest pack you can find. Right-sizing keeps you comfortable and honest about what you carry.
Hiking Backpack Size Guide FAQ
What size hiking backpack do I need?
It depends on trip length. Day hikes suit about 10 to 30 liters, overnight trips 30 to 50, and multi-day backpacking 50 or more. Within each range, your gear volume and how light you pack set the exact number. Match the capacity to how you actually hike.
What does the liter rating mean?
It is the pack’s total carrying volume, the space inside for your gear. A higher number means more room, so 20 liters holds a day’s essentials while 60 liters holds days of camping gear. It measures space, not weight, though a bigger pack filled up carries more.
What size is best for day hikes?
Roughly 10 to 30 liters. The smaller end, 10 to 20 liters, holds essentials for a shorter outing, while 20 to 30 liters fits more water, layers, and extras for a longer or fuller day. Most day hikers are well served somewhere in this band.
How big a pack for an overnight trip?
Generally 30 to 50 liters, enough to carry sleeping gear, shelter, food, and extra clothing for one night out. This range steps up from a daypack to hold the camp gear an overnight requires, and larger packs in this band add features for carrying more weight.
Is a bigger backpack better?
No. A large pack invites you to fill it, adding weight for gear you may not need, and a half-empty oversized pack lets the load shift and hurts comfort. Sizing the pack to your actual needs, so it is comfortably full, is better than buying extra capacity.
Should I size up for occasional bigger trips?
Usually it is better to size for your normal hiking and adapt for rare bigger trips than to carry a huge pack every day. If most of your hiking is day trips, a daypack fits your real life, and you can handle the occasional overnight separately rather than oversizing daily.
Does pack size affect weight?
Indirectly. The liter rating measures space, not weight, but a bigger pack tempts you to carry more, which adds weight, and larger packs themselves weigh a bit more empty. Right-sizing helps keep the loaded weight sensible by not giving you extra space to fill needlessly.
