What Liter Backpack for Backpacking: Choosing the Right Size

Table of Contents

1. Introduction
2. Understanding Backpack Volume
3. The Liter Scale: A Trip-by-Trip Breakdown
4. Factors That Change Your Liter Needs
5. Fit vs. Volume: A Critical Distinction
6. How to Measure Your Torso
7. Packing Efficiency: Making the Most of Your Liters
8. Common Myths About Backpack Size
9. Choosing Your Next Pack with BattlBox
10. Conclusion
11. FAQ

Introduction

You are standing in the middle of your living room, surrounded by a mountain of gear. There is a tent, a sleeping bag, a stove, and enough dehydrated meals to last a week. The only thing missing is the container to hold it all. Choosing the right volume is one of the most critical decisions you will make before hitting the trail. If you pick a pack that is too small, you will be forced to leave essential safety gear behind. If you pick one that is too large, you will likely overpack and carry unnecessary weight up every incline. At BattlBox, we know that the right gear only works if you can actually carry it, so it helps to choose your BattlBox subscription. This guide will break down exactly what liter backpack for backpacking you need based on your trip length, the season, and your personal gear style.

Understanding Backpack Volume

Backpack size is almost always measured in liters. This refers to the total internal volume of the pack, including the main compartment and often the permanent side pockets. If you see a backpack named with a number, like the "Osprey Atmos 65," that number tells you the liter capacity. If you want a broader look at packing strategy before you buy, start with How to Pack for Backpacking Travel.

For those who struggle to visualize a liter, use the Nalgene bottle trick. A standard wide-mouth Nalgene is exactly one liter. If you have a 50-liter pack, imagine pouring 50 Nalgene bottles worth of water into the bag. That is the amount of space you have to work with.

Quick Answer: For most backpackers, a 50 to 65-liter pack is the "sweet spot" for a 2-4 day trip. For day hikes, 10-30 liters is sufficient, while expeditions or winter trips often require 70 liters or more.

Liters vs. Cubic Inches

While liters are the industry standard, some brands still use cubic inches. This is more common with tactical gear or older hunting packs. The conversion is simple: one liter is approximately 61 cubic inches. If you see a pack listed as 3,600 cubic inches, you are looking at a roughly 60-liter backpack.

Internal vs. External Capacity

Most manufacturers calculate the liter rating based on the "closed" volume of the pack. This includes the main body and the lid (or "brain"). It usually does not include the volume of external mesh pockets or what you can strap to the outside using daisy chains or compression straps. When you are deciding what liter backpack for backpacking you need, always assume you want your gear to fit inside the bag to protect it from the elements.

The Liter Scale: A Trip-by-Trip Breakdown

The length of your trip is the primary factor in determining volume. More days on the trail mean more food and potentially more fuel.

Daypacks (10–30 Liters)

These are designed for single-day adventures where you return to your vehicle or a basecamp at night.

• 10–20 Liters: Ideal for "fast and light" adventures, mountain biking, or short summit runs. You have enough room for a hydration bladder, a rain shell, a small first aid kit, and snacks.
• 20–30 Liters: The standard for a full-day hike. This allows you to carry the "Ten Essentials," including extra insulation, a more comprehensive first aid kit, and a full day’s worth of food and water.

Weekend/Overnight Packs (30–50 Liters)

This range is for trips lasting 1 to 3 nights.

• 30–40 Liters: This is the realm of the minimalist. To use a 35-liter pack for an overnight trip, you need high-end, ultralight gear. Your sleeping bag must be highly compressible, and your tent must be compact.
• 40–50 Liters: This is a much more forgiving range for an overnight or two-night trip. You can comfortably fit a standard sleeping pad, a two-person tent, and a small stove kit. If you want that kind of gear arriving regularly, choose your BattlBox subscription.

Multi-Day Packs (50–70 Liters)

This is the most popular category for traditional backpacking. These packs are designed for 3 to 5 nights in the backcountry.

• 50–60 Liters: Perfect for a 3-day trip. You have enough room for several days of food, extra clothing, and a more robust cooking setup.
• 60–70 Liters: If you are out for 5 days or like to bring a few "luxury" items like a camp chair or a larger camera, this is your range. This volume also allows you to carry bulkier, more affordable gear that doesn't compress as tightly as ultralight alternatives. If your loadout starts to look more like a full camp setup, browse our Camping Collection.

Expedition Packs (70 Liters and Beyond)

These are "load haulers" designed for trips lasting a week or longer.

• 70–85 Liters: Necessary for long-distance treks where you cannot resupply frequently.
• 85+ Liters: Usually reserved for winter expeditions where bulky insulation and four-season tents are required, or for group leaders who are carrying extra gear for children or less-experienced hikers.

Factors That Change Your Liter Needs

The length of the trip isn't the only variable. Your environment and your personal approach to the outdoors will shift your volume requirements.

1. The Season

Winter gear is bulky. In the summer, your sleeping bag might be the size of a loaf of bread, and your "insulation" is a light windbreaker. In the winter, your -20°F down bag might take up half of a 60-liter pack on its own. You also need to carry more fuel to melt snow for water and more layers to stay safe. Generally, you should add 10 to 20 liters to your pack size if you are transitioning from summer to winter backpacking.

2. Gear Bulk (The "Big Three")

Your "Big Three" refers to your tent, your sleeping bag, and your sleeping pad. These items take up the most space.

• Ultralight Gear: If you use a quilt instead of a bag and a trekking-pole-supported tent, you can often fit a 5-day trip into a 45-liter pack.
• Conventional Gear: If you are using a standard synthetic sleeping bag and a freestanding tent with aluminum poles, you will likely need at least 60 liters for that same 5-day trip.

3. Shared vs. Solo Gear

If you are hiking with a partner, you can split the weight and volume of shared items. One person carries the tent body, while the other carries the poles and the stove. This "division of labor" can allow both hikers to use smaller, 40-50 liter packs even on multi-day trips.

4. Bear Canisters

In many National Parks and wilderness areas, bear-resistant food canisters are mandatory. These hard-sided plastic or carbon fiber bins do not compress. They take up a massive amount of internal volume (usually around 10–12 liters). If you plan to hike in "bear country," ensure your pack has enough volume and a wide enough opening to accommodate a canister.

Key Takeaway: Don't buy your pack first. Lay out all the gear you intend to take, then find the pack that fits that specific loadout with a small amount of "breathing room" left over.

Fit vs. Volume: A Critical Distinction

A common mistake is assuming that a "Large" pack means it has more liters. This is not how it works.

• Volume is how much the bag holds (e.g., 60 liters).
• Fit is how the bag sits on your body (e.g., Small, Medium, or Large frame).

Most high-quality backpacks come in different frame sizes based on your torso length, not your height. You could be 6 feet tall but have a short torso, requiring a "Small" frame. Conversely, a shorter person with a long torso might need a "Large" frame.

When you increase the volume of a pack, you are increasing its capacity to carry weight. A 70-liter pack will have a much beefier suspension system and a thicker hip belt than a 35-liter pack because it is designed to carry 40+ pounds comfortably. Never try to "overstuff" a small pack with heavy weight; the suspension will collapse, and all that weight will fall directly on your shoulders.

How to Measure Your Torso

To find your fit, you need to measure the distance from your C7 vertebra (the bony bump at the base of your neck when you tilt your head forward) down the curve of your spine to the point across from your iliac crest (the top of your hip bones).

1. Step 1: Tilt your head forward to find the C7 vertebra.
2. Step 2: Have a friend run a flexible tape measure from that point down your spine.
3. Step 3: Place your hands on your hips so you can feel the top of your hip bones.
4. Step 4: Measure to the point on your spine that is level with your thumbs.

Packing Efficiency: Making the Most of Your Liters

Sometimes the answer to "what liter backpack for backpacking" isn't a bigger bag, but better packing. If you organize your gear correctly, you can often drop down a size in volume. For a closer look at how packing choices affect your loadout, read How to Filter Water Backpacking.

The Zone Method

• Bottom Zone: Large, bulky items you won't need until camp. This is where your sleeping bag and extra camp clothes go.
• Middle Zone: Your heaviest items. This includes your food bag, water reserves, and stove. Keep these close to your spine to maintain your center of gravity.
• Top Zone: Essential items you might need on the trail. Put your rain gear, Adventure Medical Ultralight/Watertight .9 Medical Kit, and water filter here.
• Pockets/Lid: Small items like snacks, maps, a knife, and a rechargeable flashlight.

Note: Use compression sacks for your sleeping bag and clothing. These can reduce the volume of those items by 30% to 50%, allowing you to use a smaller liter pack more effectively.

External Attachments

If you are at maximum capacity, use your compression straps. A BattlBox 30L Dry Bag can keep loose items sealed and separate. However, avoid hanging heavy items off the back of the pack, as this will pull you backward and strain your muscles.

Bottom line: A 50-65 liter pack is the most versatile choice for most hikers, but seasonality and gear bulk are the final deciders of your specific needs.

Common Myths About Backpack Size

Myth: A bigger backpack is always better because you have more options. Fact: A larger pack weighs more even when empty and encourages "overpacking," which leads to fatigue and potential injury on the trail.

Myth: You should always buy the lightest pack possible. Fact: Ultralight packs often lack internal frames. If your gear is heavy or bulky, an ultralight pack will be much more uncomfortable than a slightly heavier pack with a proper suspension system.

Choosing Your Next Pack with BattlBox

At BattlBox, we focus on providing gear that actually performs in the field. Whether you are looking for a rugged daypack for your EDC (Everyday Carry) or a high-capacity hauler for a week in the mountains, our Medical and Safety collection helps round out the rest of your kit. Our team of outdoor professionals tests the equipment we curate to ensure it meets the demands of real-world use.

When you are ready to upgrade your kit, consider how your gear fits together. A high-quality sleeping bag from one of our missions might be more compressible than your current one, potentially allowing you to size down your next backpack. If you want more ways to keep discovering gear, BattlBucks rewards make that easier. We are more than just a subscription service; we are a community of outdoorsmen and survivalists dedicated to being better prepared for every adventure.

Conclusion

Determining what liter backpack for backpacking you need doesn't have to be a guessing game. By looking at the length of your trip, the gear you already own, and the conditions you expect to face, you can find the perfect balance of volume and weight.

• 10–30L for day trips.
• 30–50L for minimalist overnights.
• 50–70L for the average multi-day trek.
• 70L+ for winter and long-haul expeditions.

Remember that a backpack is only as good as the gear inside it and the person carrying it. Practice packing your bag at home and take it for a few short "weighted" walks before you commit to a long-distance trail. If you want a behind-the-scenes look at the kind of gear that can shape your next setup, check out our Videos. Adventure. Delivered. If you like sharing the outdoors with your crew, our Monthly Giveaway is another good next step. To get expert-curated survival and outdoor gear delivered to your door every month, choose your BattlBox subscription.

FAQ

Is a 40L backpack big enough for a 3-day trip?

A 40-liter backpack is generally considered tight for a 3-day trip unless you are using ultralight and highly compressible gear. For most people, 40 liters is ideal for a minimalist overnight or a very gear-heavy day hike. If you are a beginner with standard-sized camping equipment, you will likely find a 50 or 60-liter pack much easier to manage for 3 days. For more pack sizing context, browse our Camping Collection.

What size backpack do I need for a week-long trip?

For a trip lasting 7 days or more, most backpackers require a pack in the 65 to 75-liter range. This size provides enough room for about 10–15 pounds of food, plus all your standard camping and safety equipment. If you can resupply halfway through the week, you might be able to stick with a 60-liter pack. If you want to compare that with water planning, read How to Filter Water Backpacking.

How do I know if my backpack is too big?

Your backpack is too big if you have to pull the compression straps to their absolute limit to keep the load from shifting, or if there is a large amount of empty space at the top of the bag. An oversized pack can cause the weight to sag away from your back, putting unnecessary strain on your shoulders and lower back. It also adds unnecessary "dead weight" from the extra fabric and frame components. If you want a better sense of what belongs in a well-balanced trail kit, see The Essential Hiking First Aid Kit List.

Can I use a 65L backpack as a carry-on for a flight?

Generally, no. Most airlines have carry-on dimensions that roughly translate to a maximum of 35 to 45 liters, depending on the pack's frame height. A 65-liter backpacking pack is almost always too tall to fit in an overhead bin and will need to be checked. If you want a "one bag" travel and hiking solution, look for specialized travel packs in the 40-liter range. If you want to keep up with more BattlBox content, Refer a Friend and bring another outdoorsman along.