How Big of a Backpack Do I Need for Backpacking?

Table of Contents

1. Introduction
2. Understanding the Liter: How Backpacks are Measured
3. The 0–20 Liter Range: Minimalist and Hydration Packs
4. The 20–35 Liter Range: The Essential Daypack
5. The 35–50 Liter Range: Overnight and Ultralight Missions
6. The 50–70 Liter Range: The Gold Standard for Multi-Day Trips
7. The 70 Liter+ Range: Expedition and Winter Gear
8. Factors That Change the Pack Size You Need
9. Comparison Table: Trip Length vs. Pack Volume
10. How to Test Your Pack Size Before Buying
11. Fit vs. Capacity: The Critical Distinction
12. How BattlBox Helps You Pack Smarter
13. Conclusion
14. FAQ

Introduction

You are standing in your living room, surrounded by a sleeping bag, a stove, three days of food, and a stack of wool socks. You try to stuff it all into your old school bag, but the seams are screaming and the zipper just failed. Every outdoorsman has faced this moment of realization: the gear you have must match the container you carry. Choosing the right pack is the difference between a rhythmic, enjoyable trek and a miserable slog with a heavy, unbalanced load.

At BattlBox, we specialize in curating the essential gear you need for the field, but how you carry that gear is just as important as the gear itself. If you want that kind of gear arriving on a regular cadence, subscribe to BattlBox. Whether you are planning a quick afternoon hike or a week-long expedition into the backcountry, your pack volume is the foundation of your setup. This guide will help you decode liter sizes and determine exactly which capacity fits your specific adventure. Finding the right balance between weight and space is the first step toward self-reliance in the wild.

Quick Answer: For a standard 2-3 day backpacking trip, most hikers need a 50–70 liter pack. Day hikers should look at 10–30 liters, while those out for 5+ days or winter camping often require 70 liters or more.

Understanding the Liter: How Backpacks are Measured

Before you can choose a size, you need to understand how outdoor companies measure space. Unlike a suitcase, which is measured by inches and dimensions, backpacking packs use liters to describe volume. This is because trail gear is often irregularly shaped. A liter measurement tells you the total internal capacity of all enclosed compartments.

If you struggle to visualize a liter, use the Nalgene rule. A standard wide-mouth Nalgene water bottle is exactly one liter. If a pack is rated at 50 liters, it has the internal volume of 50 of those bottles. Some brands also list volume in cubic inches. To convert, remember that one liter is roughly equal to 61 cubic inches.

Why Volume Matters Over Dimensions Backpacks are designed to contour to your body. A rectangular pack with the same volume as a curved trail pack will feel much heavier because it pulls your center of gravity backward. By using liters as a standard, you can compare the carrying capacity of different styles—like a streamlined climbing pack versus a wide-loading trekking pack—without getting bogged down in measurements that don't reflect real-world use.

The 0–20 Liter Range: Minimalist and Hydration Packs

This range is reserved for the "fast and light" crowd. If you are carrying a pack this size, you are likely not staying out overnight unless you are an extreme minimalist with specialized, ultra-compact gear.

• 0–10 Liters: These are primarily hydration packs or lumbar (waist) packs. They are designed for trail running or mountain biking where you only need water, a few energy gels, and maybe a very thin emergency shell.
• 10–20 Liters: This is the sweet spot for a "summit pack" or a short day hike. You can fit a 2-liter water bladder, a small first aid kit, a headlamp, and a lunch.

In this category, you won't find heavy-duty suspension systems or thick hip belts because the weight is low enough that your shoulders can handle the load. These are perfect for scouting missions or quick excursions from a base camp.

The 20–35 Liter Range: The Essential Daypack

For the majority of hikers, a 20–35 liter pack is the most versatile piece of equipment they will own. This size is large enough to handle the "Ten Essentials" while remaining small enough to use as an everyday carry (EDC) bag.

What fits in a 30-liter pack?

• Full rain suit and an extra insulation layer (like a fleece or "puffy" jacket).
• 3 liters of water.
• A comprehensive first aid kit.
• Food for a full day.
• Small tools: a fixed-blade knife, a compass, and a fire starter.

Key Takeaway: If you are only going to own one backpack for general outdoor use and short day trips, go with a 25–30 liter model. It provides enough room for safety gear without tempting you to overpack.

The 35–50 Liter Range: Overnight and Ultralight Missions

This is where the transition from "hiking" to "backpacking" happens. A 35–50 liter pack is often called a weekend warrior bag. It is designed for one or two nights in the woods.

The Overnight Shift To use a pack in the 40-liter range for an overnight trip, your gear must be "packable." This means using a down sleeping bag rather than a bulky synthetic one and a lightweight, inflatable sleeping pad. We often include compact, high-value tools in our Advanced and Pro BattlBox tiers that fit perfectly in this size range.

Typical Loadout for 40 Liters:

1. Shelter: A lightweight one-person tent or a hammock system.
2. Sleep System: A compact sleeping bag and a folding or inflatable pad.
3. Kitchen: A small canister stove, one pot, and a spork.
4. Clothing: One change of socks and underwear, plus camp shoes.
5. Food: 4 to 6 meals.

If you are a beginner, a 45-liter pack might feel tight. Beginners often carry "legacy" gear—older sleeping bags or heavy tents—that takes up significant volume. As you refine your kit and move toward higher-quality, smaller items, you can downsize your pack.

The 50–70 Liter Range: The Gold Standard for Multi-Day Trips

If you ask a seasoned backpacker, "How big of a backpack do I need for backpacking?" they will likely point you toward the 55 or 65-liter mark. This is the most popular size range for a reason, and it lines up well with a lot of gear in our Camping collection. It is the "Goldilocks" zone for trips lasting 3 to 5 days.

A 60-liter pack allows you to carry conventional gear without having to play "gear Tetris" every morning when you break camp. It has enough room for a two-person tent, a bear canister (required in many National Parks), and enough food to keep you fueled for a work week in the wilderness.

Why 65 Liters?

• Versatility: You can under-pack a 65-liter bag for a weekend, but you can't over-pack a 40-liter bag for a five-day trek.
• Suspension: Packs in this range almost always feature a robust internal frame and a padded hip belt. This transfers 80% of the weight to your hips, protecting your shoulders and spine.
• Organization: You will usually see a dedicated "sleeping bag compartment" at the bottom and multiple access points (like a side zipper) so you don't have to dig through the top to find a snack.

Bottom line: For your first multi-day backpacking pack, a 60-liter model is the safest and most practical investment.

The 70 Liter+ Range: Expedition and Winter Gear

Packs over 70 liters are specialized tools. They are designed for one of three scenarios: winter camping, long-distance expeditions (7+ days), or carrying gear for others.

Winter Camping Needs Cold weather gear is inherently bulkier. You aren't just carrying a light shell; you are carrying a heavy parka, thick bibs, a -20 degree sleeping bag, and a four-season tent. These items do not compress well. If you plan on snowshoeing or winter bushcraft, you will likely need an 80-liter pack just to fit the insulation required to stay safe, which is why our Bushcraft collection is such a useful place to start.

The "Troop Leader" Scenario If you are hiking with children or less-experienced partners, you might end up carrying the "communal" gear. This could include a large family tent, extra water, or a more extensive cook set. In these cases, a 75 or 85-liter pack is necessary to haul the extra weight.

Note: Carrying a pack this large requires physical conditioning. A full 85-liter pack can easily weigh 50–60 pounds. Ensure you have practiced with smaller loads before attempting a long trek with an expedition-sized pack.

Factors That Change the Pack Size You Need

Two people going on the same three-day trip might need completely different pack sizes. Capacity isn't just about the number of days; it is about your environment and your style of movement.

1. The Season

In the heat of summer, your gear is minimal. You can sleep under a simple tarp and carry a light quilt. A 40-liter pack is plenty. In the autumn, when temperatures drop, you need more layers and a warmer bag, pushing you toward 50 or 60 liters.

2. Solo vs. Group Hiking

When you hike with a partner, you can split the "big three" (tent, stove, water filter). One person carries the tent body, the other carries the poles and the stove. This allows both of you to use smaller packs. If you are solo, you carry it all, which usually requires a bump in volume. A solid water filter is especially useful when your pack has to do more of the work.

3. Your Skill Level and "Comfort" Items

A survivalist might be happy with a wool blanket and a knife, but most backpackers want a camp chair, a thick pillow, and a French press. There is no shame in "luxury" items, but they require space. The Survival 13 is a useful read if you want a broader survival mindset.

Myth: A bigger backpack is always better because you have extra room. Fact: A bigger backpack weighs more even when empty, and the extra space usually encourages you to pack things you don't actually need, leading to unnecessary fatigue.

Comparison Table: Trip Length vs. Pack Volume

How to Test Your Pack Size Before Buying

You don't need to guess. You can determine your required volume at home with a simple exercise.

Step 1: Gather your kit. Lay out every single item you plan to take on your typical trip. Include your "consumables" like food and water.

Step 2: Use the cardboard box method. Find a large cardboard box. Measure its length, width, and depth in inches to calculate its volume (L x W x D). Divide that number by 61 to get the liter capacity.

Step 3: Pack the box. Place your gear into the box. If it only fills half the box, you can calculate the "filled" volume. This gives you a concrete number to look for when shopping.

Step 4: Check the weight. Once you know the volume, weigh the gear. If your gear weighs 40 pounds, you need a pack with a sturdy internal frame. If it's only 15 pounds, you can look at "frameless" or ultralight packs.

Fit vs. Capacity: The Critical Distinction

A common mistake is assuming that "Large" refers to the capacity of the bag. In the backpacking world, "Small," "Medium," and "Large" usually refer to the torso length of the frame.

• Capacity (Liters): How much stuff the bag holds.
• Fit (Torso Size): How the bag sits on your back.

You can be a 6'4" man who only needs a 30-liter pack, or a 5'2" woman who needs a 70-liter pack. Always measure your torso—from the C7 vertebra (the bump at the base of your neck) to the iliac crest (the top of your hip bones). A 60-liter pack that doesn't fit your torso will be agonizing, no matter how perfectly you packed it.

Most high-quality packs allow you to adjust the shoulder harness up or down. At BattlBox, we focus on gear that is adaptable. When choosing a pack, look for adjustable suspension systems that can grow with you or be tuned to your specific body shape.

How BattlBox Helps You Pack Smarter

Our mission is to put the right tools in your hands so you can head into the wild with confidence. We have shipped over 1.7 million boxes to outdoorsmen who value preparation and quality.

If you are just starting out, our Basic and Advanced tiers often include the essential items—knives, fire starters, and emergency shelters—that fit easily into a 20–30 liter daypack. As you progress to our Pro and Pro Plus tiers, you will receive higher-end camping equipment like sleeping pads, tents, and premium blades from brands like TOPS, Kershaw, and Spyderco. These are the items that define your needs for those 50–70 liter multi-day packs.

By curating gear that is functional and field-tested, we help you avoid the "junk" that takes up unnecessary space. A well-curated kit means you can often carry a smaller, lighter pack than someone carrying low-quality, bulky gear.

Conclusion

Choosing the right backpack size isn't just about the number of days you'll be on the trail. It is a reflection of your gear quality, the season, and your personal comfort requirements. For most people entering the world of backpacking, a 55 to 65-liter pack provides the perfect balance of versatility and support. It allows you to grow as an outdoorsman without needing to buy a new bag for every different trip.

Remember, the best pack is the one that disappears on your back. It shouldn't be a constant reminder of your poor choices; it should be a tool that enables your adventure. Once you have your volume dialed in, focus on the quality of what goes inside with our Emergency Preparedness collection.

If you're ready to build a kit you can rely on, consider exploring our BattlBucks rewards or subscribing to receive expert-picked gear every month. If you want another preparedness read, What To Do After A Power Outage is a good next stop. Adventure is waiting—make sure you have the right bag to carry it and subscribe to BattlBox.

"The goal isn't to see how much you can carry, but how little you actually need to be safe and comfortable."

FAQ

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

A 40L pack is sufficient for a 3-day trip if you have ultralight, highly compressible gear and are hiking in warm weather. However, for a beginner with standard gear, a 40L pack will likely be too tight, especially once you add food and water. Most people find a 50L or 55L pack more comfortable for a 3-day excursion. If you are building a hydration-focused kit, browse our Water Purification collection.

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

Generally, no. Most airlines have carry-on size limits that roughly equate to a 40L or 45L backpack, provided it isn't overstuffed. A 65L pack is usually too tall and wide for the overhead bin and will need to be checked. Always check your specific airline’s dimensions before heading to the airport.

How do I know if my backpack is too big for me?

A pack is too big if the frame extends significantly above your head or if the weight pulls you backward even when the straps are tight. If you have the load lifters and hip belt fully cinched and there is still a gap between the shoulder straps and your collarbone, the torso length is likely too long. Also, if you find yourself filling extra space with "just in case" items you never use, your volume is likely too high.

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

For a 7-day trip, a 60–75 liter backpack is the standard recommendation. This allows enough room for a week’s worth of food, which is usually the heaviest and bulkiest part of the load. If you are hiking in an area that requires a bear canister, leaning toward the 70L or 75L range will make packing much easier.