What Hiking Backpack Size Do You Need? Expert Tips & Advices

A well-fitted multi-day backpack provides comfort even on challenging terrain.

Choosing the right size hiking backpack is one of the most important factors for a comfortable and safe outdoor adventure.

The backpack needs to be large enough to carry all your essential gear, yet not so large or ill-fitting that it causes pain or throws off your balance on the trail.

In this post, we’ll break down how to choose the perfect pack size for day hikes, overnight trips, and multi-day treks, with tips on men’s vs women’s fit and some beginner-friendly pack recommendations from expert reviews.

Why Backpack Size Matters for Comfort, Safety, and Capacity

Picking the right backpack size isn’t just about fitting all your stuff – it directly affects your comfort and safety on a hike.

An ill-fitting or wrongly sized pack can lead to sore shoulders, back pain, and poor weight distribution that might even cause you to stumble.

Comfort

Comfort is key: your pack should sit properly on your hips and match your torso length, so the load is supported without straining your shoulders.

A correctly sized pack lets you carry 80% or more of the weight on your hips (the body’s strongest load-bearing area) and only about 20% on your shoulders – critical for avoiding fatigue on long hikes.

Safety

Proper size also ties into safety. If your pack is too small and you end up leaving behind important gear (like a warm layer or first-aid kit), you could be vulnerable in bad weather or emergencies.

Conversely, a pack that’s too big might tempt you to overpack, making your load unnecessarily heavy. Overloading a huge pack can throw you off balance and increase risk of injury.

The right size ensures you carry enough gear for the conditions without carrying so much that it becomes a liability.

Capacity

Finally, capacity is a practical matter: how many liters of volume do you need for the type of trip you’re doing?

Backpack sizes are measured in liters (L), which indicates the volume of gear they can hold. Choosing a size suited to your trip length means you’ll have adequate room for your supplies.

In short, matching your pack’s liter capacity to your adventure (be it a short day hike or a week-long trek) will help guarantee you have what you need, and that the pack carries that load comfortably.

Below, we’ll look at recommended pack sizes by hike type – day trips, weekend overnights, and longer multi-day hikes – and suggest some proven pack models in each category. We’ll also cover the differences in men’s vs. women’s packs and how to fit and adjust your backpack for maximum comfort.

Day Hikes (Up to 1 Day)

For a typical day hike, you’ll want a lightweight, compact backpack that can hold the Ten Essentials (water, food, rain jacket, first aid kit, etc.) but isn’t overly bulky.

Most day hikers find a pack in the 15–30 liter range is ideal. According to experts at REI, daypacks under ~20L work for short hikes with minimal gear, while 20–35L packs are the sweet spot for most day hikes, providing space for food, extra clothing, and small extras like a camera.

A 30L daypack is on the larger side and can carry quite a bit (useful in winter or if you’re toting gear for kids), whereas a tiny 10L running vest would only fit water and a snack for very short outings

🎒 Recommended Daypacks:

A great example in this category is the Osprey Talon 22 (men’s version) or Osprey Tempest 20 (women’s version), which offer ~20–22 liters of capacity. These packs are consistently top-rated because they hit an ideal balance of comfort and features for day trips.

The Talon 22 is praised as “a comfortable, well-built, and versatile daypack”. It has a ventilated back panel and a real hipbelt (with pockets) for support, yet remains lightweight (under 2 lbs). The Talon/Tempest comes in multiple sizes from 11L up to 33L or even 44L, so you can pick a larger version if you need more room.

If you tend to carry heavier supplies on long day hikes, consider a slightly bigger pack with an internal frame for support. For example, the Osprey Stratos 36 (and women’s Sirrus 36) is a 36L daypack with a suspended mesh frame and ample padding. It’s extremely comfortable for all-day use and even “serviceable for light overnights” due to its capacity and support.

On the budget-friendly end, the simple REI Co-op Flash 22 (22L) is frequently recommended for casual day hikes – it’s ultralight and inexpensive while still providing enough space for the essentials.

For most day hikers, aim for that 20–30L range. It will hold your water, lunch, a fleece or rain jacket, maps, and small gear like headlamp and sunscreen.

Unless you’re carrying specialized equipment (climbing gear, DSLR camera kit, etc.), a pack much larger than ~35L is usually overkill for a single-day hike. And if you go much smaller than ~15L, double-check that you can still fit all critical safety items.

Overnight & Weekend Trips (1–3 Nights)

Stepping up to overnight hikes or weekend backpacking trips (anywhere from a single night out up to about three nights), you’ll need a higher-capacity pack to haul camping gear – think sleeping bag, sleeping pad, shelter (tent), stove, food, and extra clothing layers.

For these short backpacking trips, a 30–50 liter backpack is the general recommendation. The exact size you need depends on how compact/lightweight your gear is and how many nights you’ll be out.

• 1 night (overnight): Packs on the smaller end (around 30–40L) can work if you have relatively compact gear or in mild conditions. For example, an efficient overnight backpacker with modern ultralight gear might get away with a ~40L pack for a summer single-night trip

• 2–3 nights (weekend): Aim for somewhere in the 40–50L range to comfortably fit your shelter, sleeping bag, cooking kit, and food. A 50 liter pack is a common choice for weekend trips, offering a bit of wiggle room so you’re not cramming everything in tightly.

🎒 Recommended Weekend Packs:

One of the most popular models in this mid-size category is the Osprey Atmos AG 50 for men (or Osprey Aura AG 50 for women). These are 50-liter versions of Osprey’s renowned Atmos/Aura series.

The Atmos/Aura packs are often rated as some of the best all-around backpacking packs due to their ventilated “Anti-Gravity” suspension and comfortable carry. In fact, the larger 65L version was named “best overall backpacking backpack” by Switchback Travel, and reviewers note that the design works great for anything from quick overnights to extended trips.

The 50L model is essentially the same design in a smaller capacity, ideal for weekends. It provides plenty of organization (multiple pockets, sleeping bag compartment) and an adjustable harness to fit your torso.

Many users love how the Atmos/Aura carries; it “feels more like putting on a jacket than a backpack” thanks to the suspended mesh that hugs your back. (The Atmos/Aura comes in men’s and women’s versions to accommodate different body shapes, more on that later.)

Another solid choice is the Gregory Zulu 55 (men’s) or Gregory Jade 53 (women’s). These packs (around ~53–55L) hit that weekend-trip sweet spot as well. Gregory packs are known for great load support and comfort, and the Zulu/Jade series is lighter and more ventilated than their larger expedition packs, making them nice for 2-3 night trips.

Many reviewers highlight the Zulu’s dynamic FreeFloat suspension that moves with your body and its well-padded hipbelt, which make carrying 30-40 pounds feel comfortable. Outdoor Gear Lab notes that the Zulu “offers a nice balance between weight and comfort” for weekend backpacking, though it might not be as ultralight as some competitors.

If you’re looking for a value option, the REI Co-op Trailbreak/Trailmade 60 (60L) is often recommended for beginners on a budget. It’s a relatively simple pack but earned high marks as a budget backpacking backpack in expert tests, and comes in women’s sizing too. Its 60L capacity straddles the line between weekend and longer trip, giving newcomers plenty of space for gear without a huge price tag.

For an overnight or weekend trip, try not to go too large – if you opt for a 65+ liter pack for a 2-night outing, you may be tempted to bring unnecessary extras that just add weight.

A pack around 45–55 liters forces you to pack smart while still accommodating all the core gear. (If you find that your 50L pack is absolutely bursting at the seams for a 3-day summer trip, you likely need to streamline your gear or, if everything is truly necessary, consider a slightly bigger pack or more compressible gear.)

Multi-Day Treks & Extended Hikes (3+ Nights)

For multi-day backpacking trips (typically 3 to 5 nights out), and especially extended expeditions (5+ nights) or winter hikes, you’ll want a larger backpack that can handle more gear and food.

These packs are usually in the 60–80+ liter range. As a rule of thumb, multi-day trips of 3–5 nights call for something around 50–70L, and trips longer than 5 nights (or shorter trips in winter conditions) often require 70 liters or more capacity. 

The extra volume is needed to pack additional food, extra clothing layers, and bulkier cold-weather gear or a larger tent.

🎒 Recommended Extended-Trip Packs:

A benchmark for this category is the Osprey Atmos AG 65 (men’s) and Osprey Aura AG 65 (women’s), which are ~65-liter packs. These packs are repeatedly lauded in gear reviews – Switchback Travel calls the Atmos/Aura “a standout all-rounder” that deftly balances comfort, organization, and durability. With 65L of space, they can handle a week’s worth of gear for most people. The anti-gravity suspension on these packs is excellent for ventilation and support, and they feature an easily adjustable torso length and hipbelt to fine-tune the fit.

The Atmos/Aura are also extremely popular among hikers – for example, the Atmos 65 has an average user rating of about 4.7 out of 5 stars across hundreds of reviews on retail sites, reflecting its proven comfort and quality. If you want one backpack that can flex between weekend trips and week-long treks, the Atmos/Aura 65 is a great investment (you can always compress a not-full pack down).

If you know you’ll be doing very long trips or carrying extra-heavy loads (like guiding a group or winter camping with a -20°C sleeping bag and lots of fuel), you might go even bigger – e.g. 70, 75 or 80L. The Gregory Baltoro 75 (and women’s Gregory Deva 70) is a classic choice for those needing to haul serious weight. These Gregory packs are a bit heavier themselves (~5 lbs empty) but are built to carry 40+ lb loads with ease.

In testing, the Baltoro 75 proved to be “one of the most comfortable and feature-rich designs on the market” with a highly customizable hipbelt and shoulder straps that are great for achieving a perfect fit. In other words, if you plan to pack everything including the kitchen sink, a pack like the Baltoro/Deva will support the weight and remain stable.

Many long-distance hikers and weekend “luxury” campers alike appreciate the Baltoro’s sturdy suspension for heavy gear. Another plus in this range: some large packs come with removable daypacks or top-lid pockets that convert to hip packs – useful for day excursions from basecamp. For example, the Deuter Aircontact Core 70+10 and Osprey Aether 70 are other respected models around 70L, featuring robust frames and the ability to expand or detach a small pack.

Keep in mind, bigger isn’t always better – you should choose a pack size that fits the kind of trips you actually plan to do. If most of your outings are 3-4 days, a ~60L pack is usually sufficient.

Moving up to 80+ liters is typically only needed for expeditions, winter trips, or if you’re carrying gear for others (like a parent with kids, or a climber carrying ropes/pro gear).

Also, as pack volume increases, pack weight tends to increase as well (heavy-duty materials, larger frames, etc.), so an 80L pack will weigh more on your back even when empty.

Experienced backpackers often aim to streamline their gear so they can use a smaller, lighter pack for long trips. For example, some thru-hikers on multi-week journeys use 50–60L ultralight packs, but they also use very lightweight, compact gear and forego many luxuries.

As a beginner, it’s wise to err on the slightly roomier side for multi-day trips so you’re not forced to leave behind important items. Just avoid the trap of filling any unused space with non-essentials – your knees will thank you!

Below is a quick reference table summarizing backpack size recommendations by trip length, with typical gear carried:

Backpack Size Comparison Chart

Men’s vs. Women’s Backpack Sizing

Backpack manufacturers often make men’s and women’s versions of their hiking packs – and it’s not just about color or marketing. There are genuine ergonomic differences designed to better fit different body shapes. Women-specific backpacks typically have:

• Shorter torso lengths and smaller frame sizes (on average) than men’s packs, since women tend to have shorter torsos. For example, the Osprey Aura (women’s Atmos) comes in sizes to fit torso lengths ~14–21 inches, whereas the men’s Atmos covers ~16–23 inches

• Narrower shoulder strap spacing and more contoured straps. The shoulder straps on women’s packs are often set closer together and curved to accommodate the chest. Likewise, hipbelts on women’s packs are angled to wrap around curvier hips. In general, the hipbelts and shoulder straps in women-specific packs are shaped to better accommodate wider hips and bust.

• Sometimes slightly different load distribution – for instance, a women’s pack might be designed to sit a bit lower on the hips to align with a lower center of gravity.

Men’s/unisex packs, on the other hand, are built for typically longer torsos, broader shoulders, and straighter hips.

Does that mean if you’re a woman you must buy a women’s pack? Not necessarily. Everyone’s body is unique, and the key is to get a pack that fits your torso length and hip size.

Many women find men’s or unisex packs that fit them well, and some men with smaller frames prefer the fit of a women’s pack. As one guide notes, “everyone’s body is a little different... I have guy friends that ended up choosing a women’s pack because it fits them the way they wanted”. The gender label is less important than the actual fit on your body.

So, use the women’s vs men’s design as a starting point: if you’re a woman of shorter stature or have a curvy build, try a women’s pack first. If you’re a tall woman or have a straighter figure, a unisex/men’s pack might feel fine.

Conversely, a smaller or short-torsoed male hiker might find a women’s pack in a neutral color that fits better than the men’s version. 

The good news is many quality packs now have an adjustable suspension or come in multiple sizes (S, M, L) for the torso, so they can be dialed in to fit either gender. For example, Osprey’s Atmos/Aura and many Gregory packs offer adjustable harness systems that slide to adjust torso length within a range.

Always check the pack’s specs for the torso size range, and if you’re close to the boundary between a S and M (or men’s vs women’s), it’s worth trying on both in store if possible.

In summary: choose the pack that fits your body best, whether it’s labeled men’s or women’s. Women-specific models exist to address common fit needs, and for most women they do improve comfort.

But individual fit trumps all – a properly fitted pack will hug your hips and shoulders comfortably, with the load balanced, regardless of gender branding.

Fitting and Adjustment Tips for Your Backpack

Even the perfect size backpack won’t feel good if it isn’t adjusted properly. Beginners often don’t realize that there’s a specific sequence to adjusting a pack for optimal comfort. Here are some essential fitting and adjustment tips:

• Measure Your Torso Length: Before buying a pack, measure your torso to ensure you get the right size. Your torso length is measured from that bony bump at the base of your neck (the C7 vertebra) down to an imaginary line drawn between the top of your hip bones (iliac crest). This measurement (in inches or cm) is what pack manufacturers use to size their frames (not your overall height!). For example, a “Medium” may fit an 18–20″ torso, a “Large” 20–22″, etc., depending on the brand. Knowing your torso size will guide you to the right pack size, or the right adjustment setting on an adjustable pack. Also measure your hip circumference along the top of your hips, since the hipbelt must accommodate that (most packs’ hipbelts fit a range, like 26–45″ hips). If your measurements are between sizes, it’s best to try on packs in person if you can, to see which feels better.

• Pre-pack some weight: When adjusting your backpack, put some weight in it – ~15 lbs (6–7 kg) is often suggested to simulate a real load. Empty packs don’t sit the same way as loaded ones. Loosen all the straps a bit before you put it on.

• Hipbelt comes first: Always start with the hipbelt, because this is where most of the weight should ride. Put the pack on your back and position the hipbelt so that the padding rests over your hip bones (the iliac crest) – roughly the mid-section of the padded wings should cover that top-of-hip area. Buckle the hipbelt and cinch it tight enough to be secure without uncomfortably pinching. The goal is a snug fit that carries the weight on your hips. You can tell it’s right if about 80% of the pack’s weight feels supported by your hips and the belt’s padding is cupping the top of your pelvic bones. If the belt is too high (above your iliac crest) or too low (sliding over your butt), adjust the shoulder straps (next step) to reposition it. On a correctly sized pack, the padded portion of the hipbelt will extend slightly past the front of your hip bones; you also want a little gap (~1 inch) on each side of the central buckle so you’re not tightening all the way (if you are, the belt might be too large – some packs offer interchangeable smaller belts).

• Shoulder straps next: After the hipbelt is set, pull down on the shoulder strap ends to tighten them. The straps should wrap over and around your shoulders without any big gaps. They should be snug but not carrying the bulk of the weight – remember, your hips do that. Think of the shoulder straps as simply keeping the pack close to your back and balanced; if they’re digging in excessively, the hipbelt might be too loose or the torso length might need adjustment. As a guideline, the spot where the shoulder straps attach to the pack (the anchor point) should sit about 1–2 inches below the top of your shoulders (around the top of your shoulder blades). If that anchor is way above or below your shoulders, your pack’s torso length needs tweaking or the pack might be the wrong size. Once the shoulder straps feel good, you should feel the pack pulled against your back with no gap, but you should still be able to shrug your shoulders comfortably. If your shoulders are carrying more than about 20% of the load or you feel a lot of pressure there, re-check your hipbelt tightness and torso fit.

• Load-lifter straps: These are the small angled straps at the top of your shoulders, linking the top of the pack frame to the shoulder straps. Gently tighten the load lifters so they pull the pack slightly toward your upper back. Ideally, they should form roughly a 45° angle between your shoulder and the pack body. They don’t need to be super tight – just taut enough that there’s no slack and the pack isn’t pulling backward. Over-tightening load lifters can actually hurt your shoulder rotation and create neck strain. A snug 45° is perfect: it will stabilize the load and keep the pack from swaying. If you see a gap between your shoulder and the shoulder strap padding when you tighten these, you’ve probably overdone it (loosen them a bit).

• Sternum strap: Lastly, buckle the chest (sternum) strap across your upper chest. Slide it up or down to a comfortable height, approximately an inch below your collarbone. Its job is to keep the shoulder straps in place and prevent them from slipping off outward, especially when moving around. Cinch the sternum strap until it’s secure but not squeezing your chest. You should be able to take deep breaths without feeling constricted. Over-tightening the sternum strap is a common rookie mistake – it can distort the fit of the shoulder harness and even impede breathing. So just snug it enough that you feel the shoulder straps are pulled in slightly, and no more.

After these steps, your backpack should feel evenly balanced and comfortable. Walk around and make small tweaks as needed.

Experienced hikers often fine-tune strap tension on the go – for example, loosening the shoulder straps a tad on uphill climbs to allow more breathing room, then tightening them on downhill sections for stability.

You’ll develop a feel for when to adjust what. But as a beginner, if you follow the above fitting sequence, you’re already miles ahead in terms of getting the pack to work with your body, not against it.

Pro Tip: If possible, get fitted at an outdoor gear shop. The staff can measure your torso and help you try on packs with weight. They might also have interchangeable hipbelts or shoulder harnesses to swap, ensuring you get the best fit. Once you have your pack, practice packing it and adjusting it at home before your big trip. It’s much easier to learn to adjust load lifters in your living room than on a windy mountain pass!

Conclusion

Choosing the right size hiking backpack might seem overwhelming at first, but with these guidelines you can confidently pick a pack that suits your adventures.

To recap, match the pack’s capacity to the length of your trip (day packs vs. multi-day packs have very different volume needs), and always prioritize fit (torso length and hipbelt sizing) for comfort.

Refer to expert gear reviews and user feedback – the models we highlighted (from Osprey, Gregory, REI Co-op, etc.) are all well-loved packs with proven track records.

Ultimately, the best backpack for you is one that fits you well and carries everything you need for a safe, enjoyable hike. With the right pack on your shoulders, you’ll be ready to hit the trail and focus on the scenery – not an aching back. Happy hiking!

Sources:

• REI Co-op Expert Advice – How to Choose a Backpack & Daypack
• Switchback Travel – Best Hiking Daypacks of 2024/2025
• Switchback Travel – Best Backpacking Backpacks
• OutdoorGearLab – Best Daypack Review
• The Big Outside – Osprey Atmos/Aura AG 65 Review
• “The Right Backpack: A Good Fit is Essential to Comfort, Safety” – Howard Meyerson
• Outside Online – Backpack Fitting Tips
• REI Co-op Expert Advice – Backpack Fit & Adjustment Guide
• The Pedal Project – Guide to Backpack Sizes