45 Liter Backpacks: The Right Size For Your Hike? (+ Tips and Popular Packs)

For the right person and the right hike, 45 liters is a really interesting backpack size. I’ve seen 45-ish liter packs used for everything from complex day hikes to weekend backpacking trips to fast-and-light thru hikes. It can be a very versatile and convenient pack size if you know how to use it, and it will keep experienced backpackers on their toes when it comes to lightweight gear lists.

On the other hand, I don’t necessarily recommend a 45 L pack to new backpackers unsure of what size they need. Unless your gear list is pretty well dialed you may struggle to fit even a single night’s worth of gear into a 45 liter backpacking pack. Even with lightweight gear, your multiday food capacity will be limited. And as a day pack 45 L is more space than most people need.

So who should be hiking with a 45 liter pack, how much gear will fit inside it, and which models should you consider? Read on!

Related: Guide to Choosing a Backpack Size for Hiking

When you buy through affiliate links in this post, I may earn a small commission. Thanks for your support! I always offer unbiased opinions based on real experience from the road and trail. Learn more.

Is 45 liters the right pack size?

Wondering whether 45 liters of backpack space is too much, too little, or just right for your needs? Here are a few ways to think about it.

How big is a 45 liter backpack?

Backpack sizes are usually measured in a unit of volume called liters. A typical Nalgene or Smartwater bottle, for example, each hold 1 liter of water. A 45 liter backpack would, in theory (don’t try this at home) hold 45 liters of water if you filled it full and it didn’t leak. This may or may not include pockets on the sides, back, or hip belt, depending on the pack manufacturer.

In more familiar (and drier) terms, the dimensions of a typical 45 L pack are around 28″ x 12″ x 12″. That’s a pretty convenient size, big enough to carry some serious stuff but not big enough to be unwieldy. On hikers with smaller bodies especially, this size pack won’t tower over your head or make you feel double-wide.

Is 45 liters big enough for backpacking?

If you’re new to backpacking, the short answer is most likely no, 45 liters is not big enough for a backpacking pack. It can work well in some cases though. Does this sound like you?

  • You already have a fairly dialed lightweight backpacking gear list.
  • You’ll only be out for a 2 or 3 day trip, so you don’t need to carry too much food (and you don’t need a bear canister).
  • You’re backpacking in a warm climate and don’t need much bulky warm gear (puffy jacket, warm sleeping bag, Gore-Tex rain jacket, etc).
  • The terrain is straightforward and you won’t need any technical gear (ice axe, rope, etc).

With a few rare exceptions, most people will struggle to fit all their backpacking gear into a 45 liter hiking pack unless all of the above points are true. I usually recommend that new backpackers who want to keep their options open start with a pack in the 55 – 65 liter range.

Have I talked you out of a 45 liter backpack? Hop over to my post on 65 Liter Backpacking Packs and see if that’s a better fit.

If you’re feeling really ambitious about streamlining your gear list, you may prefer an ultralight 40 liter pack. Depending on how you measure volume (pockets, extension collar, etc) some of those packs have a similar volume to the ones in this list.

When thru hiking a remote route like the Colorado Trail, it would be hard to fit the necessary food for some 5-6 day sections into a 45 liter pack unless your gear list is very lightweight. (Shown here: 68 liter ULA Circuit backpack.)

How much does a 45 L hiking backpack hold?

As with so many things, the real answer is “it depends.” People often think of pack size in terms of days, as in “how many days is a 45 liter pack good for?” But the most important factor, in my opinion, is how lightweight and streamlined your gear is.

If you don’t at least have a down sleeping bag or quilt, a tent weighing under three pounds (ideally less for solo hikers), and a lightweight sleeping pad, a 45 liter pack is too small.

Food is also an important factor. The number of days matters, and so does how carefully you choose and pack your food. Experienced backpackers are able to pack more in less space by choosing calorie-dense food and packaging it carefully.

Here are some examples of what might fit in a 45 liter hiking pack:

  • An ultralight 3-season gear list + 5 days of trail-optimized food
  • A lightweight 3-season gear list + 3 days of trail-optimized food
  • A “traditional” (not lightweight) 3-season gear list if tent or sleeping bag is strapped to the outside, + 2 days of food
  • Gear for a very long, cold, and/or semi-technical day hike with room to spare

Dedicated ultralight backpackers can stuff 5 days of food and a full 3-season gear list into a 45 liter hiking pack. They may even thru hike with this setup for weeks or months; I met some on the Arizona Trail, for example. But it takes some serious optimization and some money too, since the lightest of ultralight gear ain’t cheap.

Related: What’s the Best Pack Size for Thru Hiking?

If your gear is a little bulkier, you may still be able to make a 45 liter backpack work by strapping a large item (like your tent or sleeping bag) to the outside. Some packs have generous mesh pockets that aren’t included in the volume measurement and can be stuffed to the gills for extra space.

One way to stretch the capacity of a pack that’s a little too small: strap things to the outside. (Shown here: a 68 liter pack stuffed for a long resupply on the Colorado Trail).

Is 45 liters too big for a day hiking pack?

Yes, 45 liters is more space than most people will need in a day hiking pack. The sweet spot for day packs is more like 15 – 30 liters, which is enough space for a day’s worth of food and water, warm layers or rain gear, safety essentials, and other small items.

That said, a 45 liter pack is on the small side for multiday backpacking, which makes it better suited for day hiking than most backpacking packs. If you have a 45 liter pack that’s comfortable and fits you well, especially if it’s a lightweight minimalist style, there’s no reason you can’t day hike with it.

Especially if you’re tackling a long day hike or preparing for tumultuous weather, you’ll be glad to have the extra space. Some packs even have compression straps that can be cinched down to make a smaller load more comfy and stable inside a larger pack.

Can a 45 liter hiking pack be carry-on luggage?

If you often travel to faraway lands for your hiking adventures (lucky you!) a 45 liter pack is right on the border of being carryon-friendly.

The standard carry-on dimensions for most U.S. airlines are around 22″ x 14″ x 9″. If stuffed full, a 45 liter hiking backpack will probably not make the cut. If packed loosely and the shape is compressible, it may be able to squish into the necessary space.

Note that some packs have a stiff internal frame that can’t be compressed, which would make many 45 liter packs too tall in the longest dimension. Check the pack dimensions and carryon requirements carefully. If carryon ability is a priority for you, a 35-40 liter pack is a safer bet.

Do keep in mind that some backpacking gear isn’t carry-on friendly. Knives, stove fuel, and pepper spray are totally off-limits pretty much everywhere, while more ambiguous items like tent stakes, hiking poles, and stoves can be hit or miss.

Styles of Backpacking Packs

Though 45 liters is 45 liters, it’s important to choose the style of pack that best suits the weight of your gear and your preference for streamlined versus feature-rich organization.

Backpacking packs fall into two general categories: traditional and lightweight. The lightweight category can further be divided into lightweight and ultralight, though the line can be fuzzy. Pay attention to the weight of the pack itself, and the recommended max load, to find the right balance of comfort and weight savings. The max recommended load often exceeds the max “comfort load” by 5-10 pounds. In other words, the pack can handle that much weight, but your back and shoulders may not be able to.

Traditional: Packs in the 3-5 pound range tend to have more pockets, compartments, and features. They’re designed to carry a heavier load in relative comfort thanks to additional padding, ventilated back panels, and a more robust suspension system that transfers weight to your hips. At the 45 liter size it’s rare to need all this extra pack material since there just isn’t that much space for a heavy load. If you’re going to pare down your gear list so it fits into 45 liters, why add a few extra pounds of pack weight?

Lightweight: Packs weighing roughly 2-3 pounds are more minimalist and work best for lightweight gear, but can still offer a reasonable amount of comfort and features. If your base weight is under 20 pounds or so, this style of pack is worth considering.

Ultralight: I’m arbitrarily defining this category as weighing less than 2 pounds. Ultralight packs achieve this by being made from very light fabrics, having a very basic design, or both. It’s best to have a base weight under 15 pounds, ideally closer to 10-12 pounds, for packs like this. They can be quite comfortable if you pack them optimally, but they’re not for everyone.

In the long run, lightening your gear list and switching to a light or ultralight pack will make backpacking a lot more enjoyable. But until your base weight is under 20 pounds, you’ll probably be more comfortable with a robust pack in the 3 to 4 pound range and a larger volume of 60+ liters.

Related: 65 Liter Backpacking Packs

Popular 45 Liter Hiking Backpacks

If you’re still thinking 45 liters is the right size for your adventures, here are some of the best 45 liter hiking backpacks to consider.

Osprey Talon 44 – Men

Price: $200

Weight: 2 lbs 15 oz

The Talon is a versatile, durable, affordable, mid-weight backpack with a breathable suspension system and a variety of pockets and features. Osprey is a leader in quality comfortable packs and this all-arounder, though not the lightest, is hard to go wrong with. There’s a women-specific companion line called the Tempest, but it tops out at just 40 liters (the Talon 44 is the largest men’s model).

Gregory Maven 45 – Women

Price: $220

Weight: 3 lbs 5 oz

Durable and comfortable pack with adjustable torso length, women-specific fit, and loads of practical pockets and features. It’s on the heavy side for a 45 liter pack, so think about your gear weight and whether the extra robustness and suspension are actually needed. The 48 L Paragon is the equivalent men’s version.

Gregory Facet 45 (Women) / Focal 48 (Men)

Price: $230

Weight: 2 lbs 8 oz / 2 lbs 9.6 oz

Gregory’s Facet / Focal pair strikes a middle ground between light weight and full-featured comfort. The well-ventilated mesh back panel looks extremely comfy, and those who like to carry water in side pockets will appreciate the unique forward-facing openings.

Big Agnes Sun Dog 45 – Women

Price: $230

Weight: 2 lbs 13 oz

The women-specific Sun Dog is part of a new line of backpacks from Big Agnes, new to the backpack space but well-known for their other outdoor gear including very popular lightweight tents. The men’s version, the Prospector, is a 50 liter pack with very similar design.

Osprey Levity 45 – Men

Price: $250

Weight: 1 lb 12 oz

Osprey’s premium ultralight pack, the Levity is designed for backpackers who enjoy optimizing their gear list and moving fast, light, and far.

Osprey Lumina 45 – Women

Price: $250

Weight: 1 lb 12 oz

The Lumina is Osprey’s female-specific version of the Levity, designed for fast-and-light hikers with a dialed lightweight gear list.

Arc’teryx Aerios 45 – Women, Men

Price: $250

Weight: 2 lbs 5 oz approx.

Arc’teryx is a relative newcomer to the ultralight backpack scene, but they’re known for quality gear and the Aerios is no exception. The unique design is partially inspired by running and fastpacking vests and will feel right at home to trail runners. The multitude of easy-access front storage pockets will be appreciated by everyone. The 45 liter size is the largest of the range and thus isn’t a pack for heavy loads.

Hyperlite Mountain Gear 2400 Windrider

Price: $320

Weight: 1 lb 14 oz

This ultralight pack is best for fast-and-light hikers with some experience paring down their gear list. The 2400 cubic inches (40 L) of internal volume and another 9.8 L of external volume put this pack somewhere in the 45-ish liter range, though it’s measured slightly differently than others listed.

Whether you’re an ultralight thru hiker, lightweight weekend warrior, or even an ambitious day hiker, a 45 liter pack can be the perfect size. If you’re just getting started backpacking, a larger pack (55 – 65 liters) will give you more wiggle room and more options. On the other hand, a 45 liter backpack will encourage you to pack light, which is always a good thing.

45 Liter Pack Comparison Table

Osprey Talon 44$2002 lbs 15 oz
Gregory Maven 45 (Women)$2203 lbs 5 oz
Gregory Facet 45 (Women) / Focal 48 (Men)$2302 lbs 8 oz / 2 lb 9.6 oz
Big Agnes Sun Dog 45 (Women) / Prospector 50 (Men)$2302 lbs 13 oz / 3 lbs 1 oz
Osprey Lumina 45 (Women) / Levity 45 (Men)$2501 lb 12 oz
Arc’teryx Aerios 45 Women / Men$2502 lbs 5 oz
Hyperlite Mountain Gear 2400 Windrider$3201 lb 14 oz
Note that weights and capacities sometimes vary slightly between sizes and genders of the same pack.

More Hiking Resources

If you’re into hiking or backpacking, you might also enjoy these:

Or, visit the complete hiking and backpacking section for lots more!

About the Author

Hi there, I’m Alissa, founder of Exploring Wild. I’ve had the pleasure of hiking the Arizona Trail, Colorado Trail, John Muir Trail, Tahoe Rim Trail, and countless shorter amazing trails throughout the US and abroad. I love solitude, big views, and a good lightweight gear setup. Learn more here.

Excited about backpacking but need help getting started? The Backpacking Trip Planner Workbook will help you start off on the right foot.

Hiking resources in your inbox?

There’s more where this came from! Sign up here for occasional emails full of inspiration and information about backpacking and hiking.

3 thoughts on “45 Liter Backpacks: The Right Size For Your Hike? (+ Tips and Popular Packs)”

  1. Great summary! I’m thinking of getting the Gregory Focal 45L pack for the TMB – I will be in the refuges and only packing a couple days of snacks at best as well as daily lunch. Think I should go smaller? I’m pretty minimal on clothing. I have a 55L Maven which will be too big.

    • For just snacks and lunch I’d go smaller, like a 30 liter day pack, but I imagine you also want space for water and maybe water filter, warm and rain layers, maybe an emergency bivy or whatever safety gear you need out in the mountains? A 45 liter pack is versatile and can be compressed for smaller loads, so I don’t see a problem with it. I personally might look more in the 35 – 40 liter range but it’s not a big difference overall. Most important thing is fit and comfort. Have fun!


Leave a Comment

Item added to cart.
0 items - $0.00