Jul 6, 2025
An Essential Guide to Backpack Sizes and Volumes
Backpack sizes are confusing. I get it. There seems to be an endless array of options and volumes (measured in liters, no less). Plus, backpacks come with so many different styles, attachments, zippers and damn pockets just don’t always make sense.
What is the difference between backpack sizes? Which one is best for me? Is there a difference between travel backpacks and the ones I might take on a weekend camping trip?
Whether you are planning your first backpacking trip or replacing luggage for a more convenient travel backpack, understanding different backpack sizes and volumes can seem daunting at first.
But it doesn’t have to be.
How Do you Measure Backpack Sizes?
How Backpack Sizes Are Measured — And Why It’s Not Like Regular Luggage
One thing that often surprises new backpackers is that, unlike suitcases, travel and hiking backpacks aren’t measured by their outer dimensions — they’re measured by volume, or carrying capacity.
That’s because backpacks aren’t rigid rectangles. Most are curved to fit your body for better comfort and balance, especially when you’re on the move. Measuring by volume gives a more practical sense of how much gear they can hold — which is especially useful when planning a long hike, camping trip, or international travel.
Liters vs. Cubic Inches: Why It Can Get Confusing
Now, here’s where it can get a little tricky: not every brand measures volume the same way.
Most backpacks are listed in liters, but you may come across a few that use cubic inches instead. Some brands include both on their sizing charts (thank you for that), but not all do.
👉 Pro tip: Get used to thinking in liters. It’s the more common and universal measurement — and once you get a feel for it, it’s much easier to shop.
What the Backpack Name Tells You
If a backpack has a number in its name, it often tells you the pack’s volume in liters.
For example:
The Osprey Aura 50L has a carrying capacity of roughly 50 liters.
Keep in mind, most companies round to the nearest liter for simplicity. It’s not always exact, but it’s a reliable ballpark.
Visualizing Liters: What Does 50L Actually Hold?
If you’re struggling to imagine how much a 50L backpack can carry — trust me, you’re not alone. Here’s a surprisingly helpful trick:
Think in Nalgene bottles.
A standard Nalgene bottle holds 1 liter of water. So, a 50L pack would theoretically fit 50 Nalgenes worth of space inside.
Of course, you won’t be stuffing water bottles into your pack — but it’s a fun and visual way to understand the volume.
How to Choose Your Perfect Backpack Size
What Size Backpack Do You Really Need?
A Practical Guide Based on Your Adventure Style
Now that you’ve got a handle on liters, numbers, and volume — it’s time to revisit the big question:
What are you actually going to use your backpack for?
If you’re new to backpacking, you might not know the answer yet — and that’s totally okay. But having a rough idea of your trip style (and your comfort limits) can help you avoid buying a pack that’s too small… or way too big.
So let’s break it down. Below is a quick and simple backpack size guide, organized by typical use cases — from quick day hikes to winter expeditions.
🧢 The Essentialist (Daypack) → 0–10 Liters
For trail runners, quick nature walks, or a short morning hike, packs under 10L are perfect. These minimalist bags typically carry:
- A water bottle or hydration bladder
- Light snacks
- A windbreaker or small jacket
- Basic first aid items
Think of it as your on-the-go grab bag — not meant for much more than the essentials.
🎒 The Transient Traveler (Long Day Hikes / Light Overnight) → 10–30 Liters
Going on an all-day hike? Planning to climb, bike, or scramble along the way? You’ll likely need more space for:
- Extra food and water
- Extra clothing layers
- Climbing gear or helmets
- First aid and emergency items
Packs in this range are also great for overnight trips in warm weather where gear needs are minimal.
✈️ The Expedition Edition (Weekend Trips / International Travel) → 30–50 Liters
This is the sweet spot for many backpackers, especially those going on:
- Weekend camping trips
- Multi-day hikes (3–5 days)
- Backpacking through Europe or Southeast Asia
A 30L–50L pack offers enough room for clothes, gear, and even lightweight sleeping systems — without being too bulky. It’s also carry-on-friendly for many airlines (though 45L is usually the upper limit).
Minimalist thru-hikers often stick to this size to keep weight down and stay mobile.
🌲 Going Off the Grid (Multi-Day / 1-Week Trips) → 50–70 Liters
If you’re heading into the backcountry for a week or more, you’ll want something roomier. A 50L–70L pack gives you space for:
- A tent and sleep system
- Cookware and food for multiple days
- Extra layers and weather protection
- A few luxury items (like a camp pillow or book)
These packs are ideal for extended treks, especially when resupply options are limited.
🏔️ Pathfinder (Winter Treks / Group Leaders / Guides) → 70+ Liters
Anything over 70L might seem excessive… until you factor in:
- Bulky cold-weather gear
- Snow boots, insulated layers, and four-season tents
- Carrying extra gear for your kids, partner, or group
- Extra safety equipment for guides and instructors
Big adventures often require big packs — just be sure you can carry it comfortably!
A Few Final Thoughts…
- Fit and capacity are not the same. A petite hiker might need a small frame but still want a 60L pack.
- Test before you commit. Try packing your gear and walking around your house or climbing stairs. You’ll quickly learn if it’s manageable.
- Weight adds up fast. Every “just-in-case” item is extra ounces on your back — and after a few miles, you’ll feel every one of them.
- Aim for balance. You want enough space to carry your gear, but not so much that you overpack just to fill it.
And finally — be patient with yourself. Choosing the right backpack is a process. You might not get it perfect on the first try, but once you do, it’s a game-changer. The right backpack isn’t just gear — it’s your mobile home on the trail, your airport companion, and your best travel buddy.
What is the Best Size for a Travel Backpack?
🧳 Backpacks Aren’t Just for Hiking Anymore
Backpacks aren’t reserved for mountain trails or multi-day hikes — they’re a traveler’s best friend, especially for long-term international travel.
Many travelers (myself included) prefer a backpack over a suitcase when bouncing between hostels, countries, or public transportation systems. Why? Because backpacks are simply more mobile, more versatile, and — if chosen right — airline-friendly.
✈️ Pro Travel Tip: Go Carry-On Size
If you’re traveling internationally, your best bet is to choose a backpack that qualifies as carry-on luggage. This way, you:
- Avoid checked bag fees
- Don’t risk lost luggage
- Save time at baggage claim
Most airlines allow carry-on luggage up to 22″ x 14″ x 9″, or a total of 45 linear inches (length + width + height).
Let’s convert that:
A 22″ x 14″ x 9″ backpack = 2,772 cubic inches = roughly 45.2 liters.
✅ So, if you want to travel carry-on only, aim for a backpack around 40–45L.
🛫 Heads up: Always double-check baggage rules before you book your flight — especially with budget airlines like Ryanair, EasyJet, or Spirit, which often have stricter size and weight limits.
✅ What’s Next?
By now, backpack sizes should feel a little less overwhelming.
Once you’ve narrowed down the right capacity for your adventure, the next critical step is getting the right fit.
Because trust me — nothing can ruin an epic trip faster than a pack that digs into your shoulders or doesn’t balance properly. Whether you’re wandering European cities or hiking through national parks, fit matters just as much as size.
And the best part? You can figure it out yourself — with a little research, some try-ons, and maybe a few test walks around the block.
If you found this post helpful, consider sharing it with a fellow traveler or bookmarking it for future trips. Your back (and your baggage fees) will thank you later.
Want a follow-up post about how to fit and adjust your backpack properly? Let me know — I’d love to write one!
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