Tactical backpacks are essential for many activities, from daily use to outdoor adventures and military missions. And, picking the right size is important. A backpack that’s too small would not hold everything you need, while one that’s too big could weigh you down unnecessarily.
Let’s dive into tactical backpack capacities, starting with the smallest and working up to the largest, to help you make the right choice.
What Does Backpack Capacity Mean?
Backpack capacity refers to the amount of space inside the bag, usually measured in liters (L) or cubic inches (cu in).
This figure accounts for all compartments combined, including the main compartment, side pockets, and any attached pouches.
It’s important to understand that capacity, size, and volume are related but not the same:
- Capacity: This is the storage space available for your gear and is the most common way to compare backpacks.
- Size: This refers to the external dimensions of the backpack, which affect how it fits your body or meets airline carry-on requirements.
- Volume: This is the total internal space, calculated mathematically, and is the technical basis for capacity measurements.
For example, a backpack might have a 40L capacity (storage space), be 20 x 12 x 8 inches in size (external dimensions), and a volume of 2,400 cubic inches.
While these terms are closely related, capacity is what matters most when choosing the right backpack for your needs.
Now that we’ve clarified what capacity means and how it differs from size and volume, let’s look at how backpack capacity is measured. 
Measuring Backpack Capacity in Liters
Liters are a metric measurement of volume, widely used worldwide.
They represent the total volume of all the compartments, including the main compartment, side pockets, and additional pouches.
How to Calculate Capacity in Liters
To estimate a backpack's capacity in liters, measure the length, width, and height of its main compartment in centimeters.
Multiply these numbers to get the volume in cubic centimeters (cc), then divide by 1,000 to convert to liters:
Example: If the main compartment is 50 cm tall, 30 cm wide, and 20 cm deep:
50×30×20=30,000 cc
30,000 cc÷1,000 =30 liters
This gives you the backpack's capacity in liters. Manufacturers often use foam blocks or beads to fill the compartments and calculate this total volume.
Measuring Backpack Capacity in Cubic Inches
Cubic inches (cu in) are a standard unit of volume in the United States.
If you see a backpack’s capacity listed in cubic inches, it’s the same concept as liters but measured using the imperial system.
How to Calculate Capacity in Cubic Inches
Measure the length, width, and height of the main compartment in inches. Multiply these three dimensions to get the total cubic inches.
Example: If the main compartment is 20 inches tall, 12 inches wide, and 8 inches deep:
20×12×8=1,920 cu in
This gives you the total capacity in cubic inches.
Converting Between Liters and Cubic Inches
If you want to compare a backpack's capacity between liters and cubic inches, you can easily convert between the two:
1 liter ≈ 61 cubic inches
1 cubic inch ≈ 0.016 liters
Examples:
A 30L backpack: 30×61=1,830cu in
A 2,000 cu in backpack: 2,000×0.016=32 liters
While this guide focuses on tactical backpacks, the principles of capacity measurement apply to other tactical gear, such as duffle bags, hydration packs, and rucksacks. Choosing the right capacity ensures you’re prepared for any mission or adventure.
Small Tactical Backpacks: 9L–20L
Small tactical backpacks range from 9L to 20L. These are perfect for carrying a few essential items without extra bulk.
Common Uses
- Everyday carry (EDC): A 9L tactical backpack is great for items like a wallet, phone, flashlight, or first aid kit.
- Short outdoor trips: A 15L to 20L bag can hold water, snacks, and a light jacket, making it ideal for quick hikes.
Pros and Cons
Pros:
Lightweight and easy to carry.
Compact design fits well in crowded spaces.
Cons:
Limited storage space, so it’s not suitable for carrying larger items.
If you’re looking for something small, a 9L tactical backpack is a great start. It’s versatile and ideal for those who don’t need to carry much.
Medium Tactical Backpacks: 20L–40L
Medium backpacks, often 20L to 40L, are the most versatile. They can handle a wider range of activities while still being manageable in size.
Common Uses
- Day trips: A 20L tactical backpack can hold a change of clothes, water bottles, and food.
- Commuting: These backpacks often include compartments for laptops and other work essentials.
- Tactical missions: A 30L tactical backpack can carry tools, ammunition, and extra gear.
Pros and Cons
Pros:
Balances capacity and comfort.
Suitable for various activities, from work to outdoor adventures.
Cons:
May feel small for longer trips or missions.
If you’re unsure about which size to choose, a 20L or 30L tactical backpack is a safe option. It offers enough room for most needs without being overly bulky.
Large Tactical Backpacks: 40L–65L
Large tactical backpacks, ranging from 40L to 65L, are built for extended trips and heavy-duty use. They provide ample space for carrying everything you might need.
Common Uses
- Multi-day trips: A 50L tactical backpack can fit clothes, a sleeping bag, and camping gear.
- Tactical missions: Law enforcement and military personnel use these for carrying mission-critical equipment.
- Travel: These backpacks are great for packing everything needed for a weekend getaway.
Pros and Cons
Pros:
High capacity for extended trips.
Well-organized compartments for separating gear.
Cons:
Heavier and bulkier to carry.
A 40L tactical backpack is an excellent choice for those who need more storage but still want a manageable size. For longer missions, a 60L bag might be necessary.
Extra-Large Tactical Backpacks: 65L and Above
Backpacks in this range are designed for maximum storage. They are ideal for long-term use and professional tasks.
Common Uses
- Long expeditions: A 70L backpack can carry tents, cookware, and supplies for several days.
- Professional use: Military personnel often rely on these for extended deployments.
- Heavy-duty tasks: Perfect for carrying heavy or bulky items like tools or specialized equipment.
Pros and Cons
Pros:
Maximum capacity for the most demanding tasks.
Durable and robust designs.
Cons:
Heaviest and least portable option.
If storage space is your top priority, a 70L tactical backpack won’t disappoint. However, keep in mind that it can be too bulky for everyday use.
Common Features Across Different Capacities
Tactical backpacks share several features, no matter their size. These elements make them versatile, durable, and suitable for various needs.
However, the way these features are implemented can vary depending on the backpack’s capacity.
1. MOLLE System for Customization
In smaller backpacks (e.g., 9L to 20L), MOLLE webbing is often minimal, typically limited to one or two rows. It's suitable for attaching small pouches or tools like a flashlight or multitool.
In larger backpacks (e.g., 40L to 65L and above), you’ll find extensive MOLLE coverage, providing space for multiple attachments like hydration pouches, first aid kits, or even sleeping bag compartments.
2. Compartments for Organization
Small backpacks usually have one main compartment with a few small pockets for essentials like keys, wallets, or a phone.
Medium backpacks include compartments for separating gear, such as a padded laptop sleeve, a dedicated hydration bladder compartment, and mesh pockets for small items.
Large backpacks often have specialized compartments for bulky items like clothing, sleeping bags, or heavy tools, in addition to several small and medium-sized pockets for better organization.
3. Hydration Compatibility
Smaller backpacks usually have space for a compact 1-2L hydration bladder, ideal for short hikes or day trips.
Larger backpacks can carry larger hydration bladders (3L or more) and often include additional loops or straps to secure the bladder in place.
4. Comfort Features
Smaller backpacks may have simple padded shoulder straps and a thin back panel for light loads.
Medium to larger backpacks often include padded and adjustable straps, a sternum strap for stability, and even a padded waist belt to distribute weight more evenly. Larger backpacks may also have airflow systems to reduce sweat buildup on long trips.
Closing Remarks
We hope this guide to tactical backpack capacities is helpful to you.
If you’re ready to find the perfect fit, explore our collection of tactical backpacks designed for durability, comfort, and functionality.
If you’re a distributor, retailer, or wholesaler looking to source high-quality tactical backpacks, we’re here to help.
As a professional tactical gear manufacturer with years of experience, LQ ARMY specializes in durable, customizable designs to meet your business needs. Partner with us for reliable products and exceptional service.
FAQs About Tactical Backpack Capacities
What can I fit in a 9L tactical backpack?
Essentials like a water bottle, wallet, phone, and a small flashlight.
Is a 40L tactical backpack suitable for air travel?
Yes, most 40L backpacks meet carry-on size limits and can hold enough for a weekend trip.
What size backpack is best for a weekend trip?
A backpack with a capacity of 30L to 40L is ideal for a weekend trip. It provides enough space to pack essentials like clothes, toiletries, and snacks without being too bulky.
Can I use a small tactical backpack for air travel?
Yes, a small tactical backpack (9L–20L) works perfectly as a personal item or carry-on for air travel. It’s compact enough to fit under the seat or in the overhead compartment.
How do I know if my backpack is too heavy?
Your backpack is too heavy if it feels uncomfortable to carry or causes strain on your shoulders and back. A good rule is to keep the weight below 20% of your body weight for regular use or hiking.
What can I fit in a 20L tactical backpack?
A 20L tactical backpack can hold essentials like a water bottle, a change of clothes, a small first aid kit, snacks, and a tablet or small laptop. It’s perfect for day trips or commuting.
Is a 40L tactical backpack suitable for a 3-day trip?
Yes, a 40L tactical backpack is great for a 3-day trip. It has enough space for clothing, toiletries, and basic gear, while remaining compact enough to carry easily.
Is a 60L backpack too big for carry-on?
Most airlines don’t allow a 60L backpack as a carry-on because it exceeds typical size limits. However, you can use it as checked luggage. Always check the airline's size requirements beforehand.
Can you take a 70-liter backpack on a plane?
A 70L backpack is generally too large for carry-on and will need to be checked in. It’s best for extended trips where you need to pack a lot of gear.
What is the largest backpack allowed as a carry-on?
The largest backpack allowed as a carry-on typically measures 22 x 14 x 9 inches (around 40–45L). This can vary slightly between airlines, so always check their guidelines before you travel.
