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02 — Trail / Guide

What size daypack do I need?

Daypack volume is measured in liters, which tells you nothing until you know what has to go in it. Water and insulation are what actually set the number.

By Brijon M.Last updated How we pick
A loaded hiking daypack resting on a rock beside a trail

The short answer

Twenty to 30 liters covers almost all day hiking. Use 15 to 20 for short summer walks, 20 to 30 for a full day with layers and three liters of water, and 30 to 40 for winter days, photography gear, or carrying for a child as well as yourself.

01 — The real constraint

What actually fills a daypack

People size daypacks by imagining the gear list, which is why they size them wrong. The gear list is small. Two things dominate the volume, and both scale with conditions rather than with trip length.

Water is the first. Three liters of water is three liters of pack volume and about six and a half pounds, and on a hot or dry day you carry it. That single item can be 15 percent of a 20-liter pack's capacity. If your hiking is in a dry region or in summer heat, size the pack around the water before anything else.

Insulation is the second, and it is the one that changes by season rather than by distance. A summer day hike needs a wind shell. A shoulder-season day needs a fleece, a hard shell, a hat and gloves. A winter day needs an insulated jacket as well, and an insulated jacket compressed is still several liters. This is why the same hike needs a 20-liter pack in July and a 35-liter pack in February.

Everything else -- food, first aid, headlamp, map, phone, keys, sunscreen -- adds up to a few liters and rarely drives the decision.

  • Three liters of water is roughly three liters of volume and 6.6 pounds. Count it first.
  • Insulation for the season, compressed, is 3 to 8 liters depending on how cold it gets.
  • Food, first aid, light and navigation together are about 3 to 4 liters.
  • Leave 20 percent spare. A pack stuffed to its stated capacity does not close properly and compresses badly.

02 — The chart

Daypack size by trip type

Liters are a measure of internal volume, measured differently by different brands, so treat these as bands rather than exact thresholds. Season matters more than distance.

Once a trip needs a shelter and a sleeping bag, you have left daypack territory: that is 50 liters and up, with a frame and a load-bearing hipbelt, and the field is in best backpacking backpacks.

TripSizeCarriesHip belt?
Short summer walk, 1-3 hours10-15 L1 L water, snack, shellWebbing strap
Full summer day hike18-25 L2-3 L water, layers, lunchLight padded belt
Full day, shoulder season25-30 L3 L water, fleece and shell, extrasPadded belt
Winter day hike30-40 LInsulation, traction, extra foodLoad-bearing belt
Day hike with a camera kit28-35 LDay kit plus lensesLoad-bearing belt
Carrying for a child too30-40 LTwo sets of water, layers, snacksLoad-bearing belt
Travel and one-bag flying35-40 LClothes for a weekStowable belt

03 — What to look for

The hip belt is the specification nobody checks

Volume gets all the attention and the suspension decides whether the pack is comfortable. Above roughly 15 pounds of load, weight needs to go onto your hips, and the belt is what does that.

There are three grades of belt and the difference is not cosmetic. A webbing strap is a stabilizer that stops the pack swinging; it transfers no weight. A lightly padded belt transfers some. A proper load-bearing belt, anchored to an internal frame or framesheet, transfers most of the load onto your pelvis, which is the only arrangement that works for a heavy winter or photography load.

Packs between 20 and 30 liters come with all three, and the pack with a webbing strap will be lighter and cheaper. That is the right choice if your loads are light and the wrong one if you carry three liters of water and a camera. Check the belt before the volume.

Is 20 liters enough for a day hike?

In summer, yes, for most people. Two liters of water, a shell, lunch and the essentials fit in 20 liters with room to close the lid. In cold weather, 20 liters stops being enough as soon as an insulated jacket goes in.

Is 30 liters too big for a day hike?

Not if it has compression straps. A well-designed 30-liter pack cinches down to carry a small load without sloshing, which makes it the most versatile single size -- summer days and winter days in one pack. The penalty is a few extra ounces of fabric. See best hiking daypacks.

What size daypack for travel?

Different question, different answer: 35 to 40 liters, because the limit is the airline personal-item or carry-on sizer rather than your back. A hiking daypack and a travel pack are shaped differently for good reasons -- see carry-on size guide and best travel backpacks.

Do I need a hydration reservoir sleeve?

If you drink on the move, yes -- a hose means you sip constantly rather than stopping to dig a bottle out, and people carrying reservoirs reliably drink more. Bottles are easier to refill and to monitor. Both approaches are covered in best water bottles for hiking.

04 — Fit

Fit matters more than size

A 25-liter pack in the wrong torso length is less comfortable than a 35-liter pack in the right one, and torso length is not correlated with height in the way people assume.

Measure from the C7 vertebra -- the bony bump at the base of your neck when you tilt your head forward -- down to the level of the top of your hip bones. That measurement, not your height, is what pack sizing charts use. Packs over about 30 liters are commonly sold in two or three torso lengths, and several brands offer a women's-specific fit with a shorter torso range, narrower shoulder straps and a differently angled hip belt.

When the pack arrives, load it with roughly the weight you expect to carry and check three things: the hip belt sits on top of your hip bones rather than on your waist, the shoulder straps wrap without a gap at the top, and the load lifters angle back at roughly 45 degrees. If the belt rides above your hips, the torso is too short.

05 — Honest limits

What we did not test, and what that means

The size bands above are arithmetic from the volume of water, insulation and standard day-hike essentials, not the result of a measurement we performed. Stated liter capacities are not comparable across brands -- there is no required standard for how internal volume is measured -- which is why the chart gives ranges and why we recommend leaving spare capacity.

Volumes, weights, suspension types and torso ranges for the four picks come from manufacturer specifications. We publish no prices; packs discount heavily at season changes and any figure would be wrong quickly. Every buy link opens a live Amazon search for the model named. Our criteria are at how we pick.

What to buy

The gear we would buy for this

Trail & Terminal earns a commission when you buy through our Amazon links, at no extra cost to you. It does not change which products we pick -- see our affiliate disclosure and selection method.

1

Best for short walks and the smallest useful size

Gregory Nano 18

Eighteen liters at well under a pound, with a hydration sleeve and a webbing hip strap. The simple one.

There is a real case for the smallest pack that works, because a small pack cannot be overloaded. Eighteen liters holds two liters of water, a shell, lunch and the essentials, and it will not let you carry the things that turn a walk into a slog.

Treat the hip strap honestly. It is there to stop the pack swinging, not to carry weight, and above about 15 pounds you will feel everything on your shoulders. For short summer walks and after-work hikes that is the right pack; for a full day with three liters of water it is not.

Specs

  • 18-liter main compartment with a hydration reservoir sleeve
  • Around 1 pound empty
  • Webbing hip strap and a breathable mesh back panel
  • Front stretch pocket and dual side water bottle pockets

Good for

  • Light enough that it disappears on your back when loaded lightly
  • Genuine ventilation on the back panel, which small packs often skip
  • Costs little and lasts, with nothing complicated to break

Bad at

  • Webbing hip strap transfers no weight -- this is a sub-15-pound pack
  • Eighteen liters fills up fast once a fleece goes in
  • No framesheet, so a badly packed load presses into your back
2

Best for the default full-day hiking size

Osprey Talon 22

Twenty-two liters with a real padded hip belt and a framesheet. The pack most day hikers should own.

If one pack has to cover the majority of day hiking, this volume and this suspension grade is the combination. Twenty-two liters absorbs three liters of water, a fleece, a shell and a full day's food, and the hip belt means that load sits on your pelvis rather than your shoulders.

Two torso sizes is the other reason it is the default. Daypack discomfort is usually a fit problem rather than a load problem, and a pack sold in one length will be wrong for a lot of people. Measure your torso before ordering. The full field is in best hiking daypacks.

Specs

  • 22 liters with an AirScape framesheet and ridged foam back panel
  • Padded, contoured hip belt with zippered pockets
  • Dual-access stretch side pockets and a large front shove-it pocket
  • Available in two torso sizes; hydration sleeve included

Good for

  • A genuine load-transferring hip belt at daypack weight and volume
  • Twenty-two liters hits the summer-to-shoulder-season sweet spot
  • The framesheet keeps the load off your spine regardless of how you pack it

Bad at

  • Heavier than minimalist packs of the same volume
  • Twenty-two liters is tight for a winter day with insulation
  • The many external pockets are useful but add complexity and weight
3

Best for winter days, camera kit, or carrying for two

Osprey Stratos 34

Thirty-four liters on a suspended mesh back panel with a load-bearing belt. The one that handles a heavy day load.

Thirty-four liters is the size where a day pack stops being a bag and becomes a carrying system. Winter insulation, traction devices and extra food, or a camera body with two lenses, or water and snacks for a child as well as yourself -- these are the loads that need a frame and a real belt.

The compression straps are what make it a sensible single pack rather than a winter-only one. Cinched down, 34 liters carries a summer load without the contents shifting, which is the usual failure of a large pack used lightly. For the cold-weather kit that fills it, see winter camping gear list.

Specs

  • 34 liters with an AirSpeed suspended mesh back panel
  • Load-bearing hip belt anchored to a peripheral frame
  • Integrated raincover, sleeping pad straps and dual ice tool loops
  • Compression straps on both sides; two torso sizes

Good for

  • Carries 25 to 30 pounds comfortably, which no 20-liter pack does
  • The suspended mesh panel keeps your back dramatically cooler
  • Compression straps cinch it down for lighter loads, so it works year-round

Bad at

  • Overkill and unnecessarily heavy for a summer day hike
  • The suspended panel pushes the load slightly away from your back
  • Thirty-four liters invites you to carry more than you need
4

Best for a pack that does hiking and travel

Osprey Daylite Plus 20

Twenty liters with a laptop sleeve and attachment points for a larger pack. The crossover option.

The crossover pack is the right answer for one specific trip shape: flying somewhere to hike. One bag that holds a laptop through the airport and water and layers on trail saves you carrying two, and the zip-on attachment to a larger pack means it rides along without being worn.

Buy it knowing it is a compromise. A dedicated hiking daypack ventilates better and carries weight better; a dedicated travel pack organizes better. If your trips are either hiking or travel but rarely both, buy for the one you do more. See best personal item bags.

Specs

  • 20 liters with a dedicated padded laptop or tablet sleeve
  • Attaches to the back of larger Osprey packs as a zip-on daypack
  • Lightly padded hip belt and mesh-covered foam back panel
  • Front shove-it pocket and dual mesh side pockets

Good for

  • Works as a personal item on a flight and as a trail daypack in the same trip
  • The laptop sleeve is a real one, not a token padded divider
  • Zips onto larger Osprey packs, which is genuinely useful for travel

Bad at

  • Compromised at both jobs -- less ventilated than a hiking pack, less organized than a travel one
  • Light hip belt, so it is a sub-20-pound pack
  • Twenty liters is tight if you want both a laptop and three liters of water

Questions

Frequently asked

What size daypack do I need for hiking?
Twenty to 30 liters covers almost all day hiking. Fifteen to 20 for short summer walks, 20 to 30 for a full day with layers and three liters of water, and 30 to 40 for winter days or a camera kit.
Is a 20L backpack big enough for hiking?
For summer day hiking, yes -- two liters of water, a shell, food and the essentials fit comfortably. It stops being enough in cold weather, once an insulated jacket and extra layers have to go in.
What size daypack for a full day hike?
Twenty-five to 30 liters if you want one pack for three seasons. That holds three liters of water, a fleece, a hard shell, food and the essentials with room to close the lid properly.
Does a daypack need a hip belt?
Above about 15 pounds of load, yes. A webbing strap only stops the pack swinging; a padded or frame-anchored belt transfers weight onto your pelvis, which is what keeps your shoulders from carrying everything.
How do I measure my torso length for a backpack?
Measure from the bony bump at the base of your neck, which appears when you tilt your head forward, down to the level of the top of your hip bones. That figure, not your height, is what pack size charts use.
Can I use a hiking daypack for travel?
For a personal item, yes, and crossover models with a laptop sleeve do both adequately. A dedicated travel pack opens flat and organizes clothing better; a hiking pack ventilates and carries weight better.

References

Back up a level

This page sits in Trail -- what you carry on your back: packs, poles, water, warmth.

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