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Choosing the right backpack size isn’t just about finding one that looks good on your back; it’s about picking a pack that truly works for what you need. I’ve found that the capacity of your backpack can make or break your experience out there—whether you’re hiking, hunting, or on a multi-day trip. A pack that’s too small will leave you wishing for more space, while an oversized pack can feel like you’re carrying around unnecessary weight (not to mention the backache that comes with it). Getting the size just right means your pack is comfortable, functional, and totally suited for your adventure.
In this post, we’re diving into the details of backpack capacity, covering everything from volume measurements to practical tips on choosing the best size for different types of trips. I’ll break down how capacity is measured in liters and cubic inches (trust me, it’s not as complicated as it sounds!) and what those measurements really mean in practical terms. I’ve also learned through trial and error that certain packs work better for specific environments, so I’ll share how terrain, climate, and hunting style play into finding the right fit.
By the end, you’ll have a solid grasp on what backpack size you need for your own adventures. Whether you’re aiming to go ultra-light, need something hefty for an extended stay in the backcountry, or are looking for a size that balances both comfort and storage, this guide will help you make an informed choice. And if you’re anything like me, you’ll find that experimenting with different sizes can be part of the fun, but it’s even better when you’re armed with some helpful tips to get started. So let’s get into it!
Understanding Volume Measurements
When it comes to backpacks, capacity is everything. It’s basically a measurement of the pack’s internal space—how much gear it can hold without you needing to strap things to the outside or stuff your pockets. Manufacturers measure this capacity in either liters or cubic inches. Think of it like measuring the volume of a container; it’s about figuring out how much can fit inside without overloading it.
What Does Capacity Mean?
In backpacking terms, capacity refers to the total volume of space inside the main compartment and any additional pockets. This volume is usually expressed in liters (L) or, sometimes, cubic inches (in³), which tells us how much gear we can fit. For example, a smaller daypack might have a capacity of around 20 liters, while a big expedition pack could be well over 80 liters. More space means more gear, but it also means more weight. So, the trick is to balance capacity with your specific needs—making sure you have enough room without carrying unnecessary bulk.
Liters vs. Cubic Inches
Most packs are measured in liters because it’s a simpler, universal way to compare capacities. However, in places like the U.S., you might see cubic inches, which can be a bit confusing if you’re used to thinking in liters. Here’s a quick tip for converting: 1 liter is roughly equal to 61 cubic inches. So, if you see a backpack labeled at 3,660 cubic inches, that’s about 60 liters. Knowing this conversion can help if you’re comparing packs from different brands that may use different units.
How Manufacturers Measure Capacity
Now, you might wonder how brands actually figure out these volume measurements. Typically, they fill the backpack with small items—like tiny balls or pellets—and measure the total volume it can hold. But keep in mind that this measurement is often based on the maximum capacity of every pocket and compartment combined. Some packs might have tons of smaller pockets, while others might focus on one large main compartment. This is why two packs labeled as 40 liters might feel quite different depending on their layout and pocket design. A more compartmentalized pack might have less usable space in the main compartment, for example, even if the total capacity is technically the same.
So, while capacity measurements give you a great starting point, it’s always worth checking the pack’s layout and pocket design to see how usable that space will be for your gear.
Different Capacity Ranges and Their Ideal Uses
Backpacks come in a huge range of sizes, and each one is designed with a specific purpose in mind. Choosing the right capacity can be the difference between a pack that feels like a second skin and one that’s a constant battle to carry. Let’s break down the most common capacity ranges and look at when and where each one shines.
10-20 Liters: Daypacks
This size range is perfect for short outings where you just need the essentials—a water bottle, some snacks, maybe an extra layer, and a small first aid kit. I grab my 15-liter daypack for quick hikes or when I’m out exploring and don’t need much more than the basics. This range keeps things lightweight and manageable, making it ideal for everyday use or a few hours on the trail.
20-40 Liters: Small Overnight Packs
When you’re planning an overnight stay or a more gear-intensive day trip, a pack in the 20-40 liter range starts to make sense. This size gives you room for a bit more, like a compact sleeping bag, a lightweight tent, and food for a night. It’s great for minimalist hikers or anyone who’s looking to keep things simple and light without feeling cramped. I often recommend this range to folks who are just getting into overnight trips and want a balance between space and ease of carrying.
40-60 Liters: Weekend and Multi-Day Trips
This is the sweet spot for weekend camping trips or two- to three-day adventures. A 50-liter pack, for instance, can carry a sleeping bag, shelter, cooking gear, and extra layers, along with a decent amount of food and water. I’ve used this size for those trips where I need enough gear for comfort but don’t want the bulk of a full-on expedition pack. It’s spacious enough to cover you for a few days, but not so large that you feel weighed down.
60-80 Liters: Extended Trips and Backpacking
When it’s time for a multi-day trip or you need to pack for a variety of weather conditions, the 60-80 liter range steps up. With this size, you can carry everything you need for an extended trip, including extra clothing, cooking gear, and a decent food supply. I find packs in this range are ideal for more remote areas where you won’t have access to resupply points and need to carry all your essentials. They’re a bit heavier, but the trade-off is worth it for the added comfort and confidence in tough environments.
80+ Liters: Expedition Packs
This is where you get into the big leagues—80 liters and up. Expedition packs are designed for serious, long-haul adventures. They’re ideal for extended backpacking trips, winter hikes where you need bulky gear, or any situation where you need to carry specialized equipment. For me, this size is reserved for extreme situations, like winter camping where I need a lot of cold-weather gear. Just be prepared: this much capacity can get heavy quickly, so make sure you really need that extra room before committing to an expedition pack.
Each of these capacity ranges has its own sweet spot, depending on the type of trip and how much you prefer to pack. If you’re new to backpacking or unsure where to start, I recommend trying out a couple of different sizes to see what feels right. With a bit of experimenting, you’ll find the range that fits your style best and gives you just the right balance of space and comfort.
Factors to Consider When Choosing the Right Capacity
Finding the right backpack size goes beyond just picking a number that sounds good—it’s about matching that capacity to your specific needs and style. Here are some key factors to consider to make sure your backpack works for you and whatever adventures you’re planning.
Trip Duration
How long you’re going to be out is one of the biggest considerations. If you’re heading out for a single day, a small daypack will probably be enough. But if you’re looking at a multi-day trip or even a week in the backcountry, you’ll need room for extra food, layers, and gear. I like to start with a simple rule of thumb: around 15-30 liters for day trips, 30-60 liters for weekend to three-day trips, and 60+ liters for longer treks. It’s a good baseline, though the final choice depends on what else you’re bringing along.
Type of Activity
Different activities require different types of gear, which impacts the size of the pack you’ll need. Hiking, for example, usually requires a moderate amount of space for essentials, while hunting might require a larger pack to accommodate things like specialized gear, optics, or even haul game. For hunting, I’ve found that having a bit more capacity (40-70 liters) gives me the flexibility to pack everything comfortably without overstuffing. Climbers, on the other hand, often prefer a sleek, low-capacity pack for gear simplicity and freedom of movement. Always think about the unique demands of your activity when choosing your pack size.
Personal Packing Style
Your packing style is another big factor. If you’re a minimalist who’s happy to skip a few comfort items, a smaller pack will work just fine. But if you’re like me and prefer to have a few extras (like a camera or an extra cozy layer), you might want to size up. Minimalist packs are great for cutting down weight, but a little extra room can make a big difference in comfort for those who like a more relaxed approach to packing.
Weather Conditions
Weather is a game changer. For trips in cold or unpredictable weather, you’ll likely need a larger pack to fit bulkier, warmer layers and extra food. Rainy conditions can mean packing a few additional items, like rain gear or waterproof bags, which all take up more room. When I’m heading out somewhere with tough weather conditions, I tend to size up by 5-10 liters to make sure I’m covered without having to strap too much gear to the outside of the pack.
Season and Terrain
The season and terrain can also impact how much you need to bring. In summer, you can often get away with lighter, smaller packs because the gear is more compact and conditions are typically more forgiving. But in winter, or if you’re heading into rugged, high-altitude areas, you’ll need to account for heavier, more durable gear. I’ve found that rocky or snowy terrain requires more equipment—things like crampons, extra water, or cooking fuel—which adds to the pack’s weight and size requirements.
Thinking about these factors can make a huge difference when choosing the right capacity. The goal is to find a backpack that’s big enough to fit what you need but not so large that you’re carrying around dead weight. A little planning goes a long way, and once you get a feel for the type of pack that suits your trips, you’ll be ready to pick the perfect size for any adventure.
Practical Tips for Estimating Your Ideal Capacity
Choosing the right backpack capacity can feel a bit like a guessing game at first, but with a few practical tips, you’ll be able to find the size that fits your gear and keeps you comfortable on the trail. Here are a few tried-and-true methods I’ve found helpful for estimating the best pack size for different adventures.
Use a Gear Checklist
Start with a checklist of the items you usually bring along. It’s a simple trick, but writing everything down can help you visualize how much space you’ll actually need. When I plan a trip, I jot down everything—sleeping bag, food, clothes, cooking gear, and those “just-in-case” items. For a day hike, you might find that 15-20 liters is plenty, but if you’re packing for a week in the mountains, that list will quickly fill up a larger 60-80 liter pack.
Test with Gear in a Store (if possible)
One of the best ways to figure out the right capacity is to test packs in a store with gear. Many outdoor stores will let you stuff a pack with weighted bags or, if you bring your own gear, you can see how it actually fits inside. I’ve done this myself when comparing sizes, and it’s amazing how different packs can feel depending on their shape and structure. Trying out packs with the weight you expect to carry gives you a real sense of whether the pack is too big, too small, or just right.
Factor in Comfort and Accessibility
While capacity is key, it’s also important to think about how comfortable and accessible the pack is when it’s fully loaded. Sometimes, I’ve packed a bag to the brim, only to find it’s tough to access things I need quickly, like a rain jacket or snacks. Packs with multiple compartments or side-access zippers can help with this, but keep in mind that the more pockets there are, the less space you’ll have in the main compartment. The ideal pack will balance capacity with good organization, so you’re not constantly unpacking to get what you need.
Consider Packing Style and Extras
If you’re someone who likes to pack extras—maybe a camera, a thicker sleeping pad, or a more extensive first aid kit—allow a little extra room to keep things comfortable. I’ve found that going just a bit bigger can be worth it for peace of mind, especially when it’s hard to predict what conditions will be like. It’s better to have a little extra space than to be cramming items into every nook and cranny, which can make the pack heavier and more awkward.
Be Willing to Experiment
The perfect pack size often comes down to trial and error. I can’t count how many times I’ve tweaked my pack size depending on the trip—sometimes even mid-season if my needs change. Don’t be afraid to experiment with different capacities until you find what really works for your specific trips. You’ll get a feel for what’s too small, what’s too bulky, and what’s just right for your own style.
Taking the time to estimate your ideal capacity and experimenting a bit can make all the difference. With the right size pack, you’ll be able to carry everything you need without feeling overloaded. And as you try out different setups, you’ll get closer to finding that sweet spot where your backpack feels like an extension of yourself, perfectly fitted to each adventure.
Conclusion: Finding Your Perfect Fit
Finding the right backpack size is a bit of a journey, but when you land on that perfect fit, it’s absolutely worth it. A well-chosen pack doesn’t just carry your gear; it helps you feel more confident, prepared, and comfortable wherever you’re headed. By understanding the basics of capacity and thinking about the type of trip, gear, and conditions you’ll face, you’re well on your way to making a smart choice.
Remember, the key is to strike a balance between enough space and comfortable weight. Too small, and you’ll feel like you’re leaving essentials behind; too big, and you’ll be hauling extra weight you don’t need. As you dial in on your ideal capacity, think of it as a work in progress. Test it out, see what feels right, and don’t be afraid to make adjustments as you go. Sometimes, the process of fine-tuning is part of the fun!
I’d love to hear about your experiences, too. Have you found a particular capacity that just clicks for your needs? Or maybe you’re still figuring out what works best? Feel free to share your thoughts or ask questions in the comments—whether you’re a backpacking pro or a first-timer, we’re all learning and exploring together. Happy packing, and here’s to finding a pack that fits you (and your adventures) just right!