Capacity in Roof Cargo Boxes: What It Is and Is It Worth It?

Roof Box Capacity Explained Simply

Capacity refers to the internal volume of a roof cargo box. It tells you how much gear fits inside. Manufacturers measure this space in cubic feet. You will see numbers like 11, 13, 14, or 30 cubic feet on product listings. These figures are not guesses. They are standardized measurements of usable space.

Understanding capacity explained helps you match the box to your needs. A 11 cubic foot box is small. It holds a few large suitcases or camping gear for a weekend trip. It fits on smaller roof racks or cars with lower weight limits. A 13 cubic foot option offers slightly more room. It is a good middle ground for families with moderate travel needs.

The 14 cubic foot size is common. It provides ample space for two adults with luggage for a week. It balances size and aerodynamics well. The 30 cubic foot box is large. It is designed for long road trips or moving items. It requires a robust roof rack system. You must check your vehicle’s weight limit before choosing this size.

Buyers care about capacity because it determines utility. If you buy a box that is too small, your gear will not fit. If you buy one that is too big, it may be hard to load. It also affects fuel efficiency. Larger boxes create more drag. They reduce gas mileage more than smaller ones.

Always check the exact cubic footage. Do not rely on vague terms like "large" or "small." Look for the specific number. Compare it to the items you plan to carry. Measure your roof rack width too. The box must fit securely. Proper capacity selection ensures your trip is organized and safe. It prevents overpacking and keeps your vehicle stable on the road.

Capacity Options Compared

11 Cubic Feet

This capacity suits compact vehicles or light loads. The Auto Dynasty 11 cu ft Hard Shell Roof Box is a clear example. Its smaller footprint keeps your vehicle’s aerodynamics intact. You get weather-resistant storage without adding significant wind noise. This size is ideal for weekend trips with minimal gear. It fits in the trunk of many sedans when removed. However, you sacrifice volume. You cannot pack large suitcases or camping equipment. Choose this if you prioritize fuel efficiency and easy parking over storage space. It is a practical choice for urban drivers who need occasional extra room.

13 Cubic Feet

A 13 cubic foot box offers a balance of space and manageability. The DNA Motoring 13 cu ft Lockable Roof Box illustrates this tier. It provides more room than compact models while remaining compatible with standard roof racks. You can fit several large duffel bags or camping gear. The lockable feature adds security for your belongings. This size is versatile for family vacations or road trips. It does not overwhelm smaller SUVs. The trade-off is that it may not fit on narrow crossbars. Ensure your vehicle’s rack system can handle the width. It is a solid middle ground for most travelers.

14 Cubic Feet

At 14 cubic feet, you gain noticeable storage without going extreme. The Garvee 14 cu ft Dual-Side Rooftop Cargo Box shows how dual access improves usability. You can load gear from either side, which is helpful in tight parking spots. This capacity handles moderate storage needs well. You can pack for a longer trip with more comfort. The dual-side opening is a practical feature for shared loading. However, these boxes are often heavier and wider. They require robust roof racks. This size is best for drivers who want extra space but still value convenience. It is a strong choice for active families.

30 Cubic Feet

Thirty cubic feet is a high-volume option for serious hauling. The FIVKLEMNZ 30 Cubic Feet Roof Bag demonstrates this capacity. It provides ample space for large luggage loads. This is ideal for moving items or extended expeditions. The soft bag design mounts easily to cars without hard racks. You get maximum utility in a flexible form. The trade-off is aerodynamics and security. Soft bags are less secure and create more drag. They are also bulkier when empty. Choose this if you need to transport many items at once. It is not for daily commuting. It is a specialized tool for heavy-duty cargo needs.

Is This Capacity Right For You

Who needs it

You should choose a roof cargo box based on your specific storage needs and vehicle size. If you have a compact car or drive frequently on short trips, a smaller capacity like 11 or 13 cubic feet is ideal. These boxes add minimal wind resistance and keep your vehicle’s aerodynamics intact. They provide weather-resistant storage without creating significant noise. This option is perfect for carrying a few bags, sports gear, or seasonal items. You get practical space without compromising fuel efficiency or handling. On the other hand, if you plan long road trips or carry bulky equipment, a larger box with 30 cubic feet is necessary. It holds much more gear for family vacations or camping trips. The 14 cubic feet option sits in the middle, offering a balance for moderate loads. Consider how much you actually pack. Do you need maximum space or just extra room for a few items? Your answer determines the right capacity.

Who can skip it

You can ignore high capacity numbers if you rarely use your roof for storage. Many drivers prefer keeping their roof clear to maintain fuel economy and vehicle stability. Large boxes create drag and increase noise, which affects driving comfort. If you only need to carry a bike rack or a kayak, a roof box is not the right tool. You should prioritize a different carrier type instead. Also, skip large capacities if your vehicle has a low weight limit. Adding a heavy, full box can exceed your car’s roof load rating. This is dangerous and may damage your vehicle. Check your owner’s manual for maximum roof weight. If you live in an area with low ceilings, a tall box might not fit in your garage. Measure your clearance before buying. For most city drivers, a roof box is unnecessary clutter. Keep your roof clear for better performance and easier parking.

Capacity Glossary Terms

Cubic Feet

The standard unit for measuring internal volume. Common sizes range from 11 to 30 cubic feet, indicating total storage space for your gear.

Shell Type

The construction material of the box. Hard shells offer rigid protection, while soft shells provide flexible, lightweight storage options for various loads.

Opening Style

How the lid accesses the interior. Single-sided opens from one side, while dual-sided allows entry from both sides for easier loading.

Load Capacity

The maximum weight the box structure can safely hold. This limit is separate from volume and ensures the box does not deform under heavy gear.

Vehicle Type

The recommended car class for the box. Compact cars suit smaller boxes, while SUVs and trucks accommodate larger, high-capacity carriers for more gear.

Water Resistance

The ability to keep rain out. Look for sealed gaskets and tight-fitting lids to protect your belongings from moisture during wet weather travel.

Security Features

Mechanisms to prevent theft. Integrated locks and key systems secure the lid, keeping your stored items safe when you are away from the vehicle.

Quick picks

Our 6 picks

1

Garvee 14 cu ft Dual-Side Rooftop Cargo Box

Best for: Dual-side access and moderate storage needs

Capacity

14 Cubic Feet (what this guide is about)

Shell Type

ABS hard shell

Opening

Dual-side

Load Capacity

165 lbs

Water Resistance

Waterproof

Security

Keys and straps

View on Amazon: Garvee 14 cu ft Dual-Side Rooftop Cargo Box Affiliate link

The Garvee rooftop cargo box provides 14 cubic feet of storage in a hard ABS shell. It features dual-side opening for access from either side of your vehicle. The unit measures 62.2 inches long and weighs 43 pounds. It supports up to 165 pounds of gear. This carrier suits drivers with roof racks who need convenient, weather-protected storage for road trips.

Pros

• Dual-side opening for flexible access
• 14 cubic feet (390L) capacity
• Hard ABS shell is waterproof and UV-resistant
• Aerodynamic shape reduces noise and fuel consumption

Cons

• Heavier at 43 pounds than many competitors
• Lower load capacity of 165 lbs compared to larger carriers
• Requires manual locking when switching sides

Good fit if

• You need access from both sides of your vehicle
• You have a roof rack with sufficient weight limits
• You prioritize weather protection for your gear

Skip if

• You require a capacity larger than 14 cubic feet
• Your roof rack cannot support 43 pounds
• You prefer a single-side opening mechanism

Verdict: The Garvee 14 CuFt Dual-Side Opening Roof Box offers convenient dual access and durable ABS construction. It fits drivers who value side access and moderate storage over maximum weight capacity.

2

DNA Motoring 13 cu ft Lockable Roof Box

Best for: Secure storage on wide crossbars

Capacity

13 Cubic Feet (what this guide is about)

Shell Type

ABS

Opening

side

Load Capacity

110 lbs

Security

key and lock

Installation

no tool assembly

View on Amazon: DNA Motoring 13 cu ft Lockable Roof Box Affiliate link

This DNA Motoring carrier offers 13 cubic feet of storage and supports up to 110 lbs. It measures 72 inches long with a 30-inch width. The ABS shell is lockable and opens from the side. It mounts to crossbars without tools. This rigid box suits those needing secure, weather-resistant cargo space for standard roof racks.

Pros

• 13 cubic feet internal capacity
• 110 lbs maximum load capacity
• Side-opening lid for easy access
• Key lock security system
• Tool-free installation on crossbars

Cons

• 72-inch length may not fit compact vehicles
• 51.6-pound weight adds roof load
• Fits crossbars only, not factory rails

Good fit if

• You need a lockable hard shell for security
• You have a vehicle with wide crossbars
• You carry bulky items needing side access

Skip if

• You have narrow factory roof rails
• You need more than 110 lbs capacity
• You want a compact 11 cubic foot box

Verdict: DNA Motoring 13 CuFt Roof Box is a solid choice for users with wide crossbars who prioritize security and side access over compact size.

3

FIVKLEMNZ 30 Cubic Feet Roof Bag

Best for: Large loads on vehicles without roof racks

Capacity

30 Cubic Feet (what this guide is about)

Shell Type

840D PVC soft bag

Water Resistance

100% waterproof

Security

Luggage lock

Installation

Straps and door hooks

Vehicle Compatibility

With or without roof rack

View on Amazon: FIVKLEMNZ 30 Cubic Feet Roof Bag Affiliate link

This soft-sided cargo bag offers 30 cubic feet of storage space with dimensions of 60 by 43 by 20 inches. It uses 840D PVC material and high-frequency welded seams to ensure it is waterproof. The design includes ten reinforced straps and six door hooks for secure mounting. You can install it on vehicles with or without existing roof racks. It weighs 12 pounds and fits seven to nine suitcases.

Pros

• 30 cubic feet capacity for large loads
• 100% waterproof 840D PVC construction
• Mounts to vehicles without roof racks
• Includes 10 reinforced straps and 6 door hooks
• Weighs only 12 pounds

Cons

• Soft shell lacks the rigid protection of hard plastic boxes
• Aerodynamic drag is higher than hard shell alternatives
• No integrated locking mechanism for the main compartment

Good fit if

• You need maximum storage volume for family trips
• Your vehicle has no roof rack or crossbars
• You want a waterproof bag for wet weather travel

Skip if

• You prefer a rigid hard shell for better aerodynamics
• You need a lockable main compartment for security
• You want a lower profile to reduce wind noise

Verdict: FIVKLEMNZ 30 CuFt Soft Roof Bag provides ample space for large luggage loads and mounts easily to cars without racks. It suits travelers prioritizing volume and weather protection over aerodynamic efficiency.

4

Auto Dynasty 11 cu ft Hard Shell Roof Box

Best for: Light loads and compact vehicles

Capacity

11 Cubic Feet (what this guide is about)

Shell Type

Hard shell, ABS

Opening

Passenger side

Load Capacity

110 lb

Water Resistance

Weather-resistant

Security

Key lock

View on Amazon: Auto Dynasty 11 cu ft Hard Shell Roof Box Affiliate link

This hard shell cargo box offers 11 cubic feet of storage with a 110 lb load limit. It features a textured ABS shell for weather and impact resistance. The design includes a passenger-side opening and a key lock system for security. It mounts to crossbars up to 13 inches wide using tool-free brackets. This unit suits travelers needing compact, secure luggage space for smaller vehicles or lighter loads.

Pros

• 11 cubic feet capacity for moderate gear
• 110 lb maximum load weight
• Passenger-side opening for easy access
• Key lock system for security
• Tool-free installation brackets included

Cons

• 11 cubic feet is smaller than the 14, 13, and 30 cubic foot options on this list
• 110 lb load limit is lower than typical hard shell competitors
• Single-side opening limits access compared to dual-side designs

Good fit if

• You need a compact box for smaller vehicles
• You prefer passenger-side access for curb loading
• You require a hard shell for weather protection

Skip if

• You need to carry more than 11 cubic feet of gear
• You want to load items from both sides
• You plan to exceed the 110 lb weight limit

Verdict: Auto Dynasty 11 CuFt Hard Shell Roof Box provides secure, weather-resistant storage for lighter loads. It fits buyers who prioritize compact dimensions and single-side access over maximum capacity.

5

VISRACK 14 cu ft Dual-Side Roof Box

Best for: Side-access loading and moderate storage

Capacity

14 Cubic Feet (what this guide is about)

Shell Type

Hard shell (ABS, acrylic)

Opening

Dual-side

Load Capacity

150 lb

Water Resistance

Waterproof

Security

Key lock with spare key

View on Amazon: VISRACK 14 cu ft Dual-Side Roof Box Affiliate link

The VISRACK roof box offers 14 cubic feet of storage in a 62.5-inch hard shell. Its dual-side opening design provides 15 inches of clearance for easy loading from either side. The ABS and acrylic construction supports 150 pounds of gear. It fits crossbars up to 3 inches wide. This model suits travelers who need flexible access without sacrificing weather protection.

Pros

• 14 cubic feet capacity
• Dual-side opening for access
• 150 lb load capacity
• Tool-free installation

Cons

• 14 cubic feet is smaller than 30 cubic feet options
• 30.2 pounds adds vehicle weight
• Only one color option available

Good fit if

• You need side access for tight parking spots
• You carry gear up to 150 pounds
• You prefer a low-profile 13.2-inch height

Skip if

• You require more than 14 cubic feet of space
• You need a hitch-mounted carrier instead
• You want a soft-sided roof bag

Verdict: VISRACK 14 CuFt Dual-Side Roof Box fits drivers who prioritize side access and moderate storage. It is ideal for weekend trips where 14 cubic feet is sufficient. It is not suitable for those needing maximum volume.

6

Mockins 30 cu ft Hitch Cargo Carrier Bag

Best for: Hitch-mounted high-volume cargo hauling

Capacity

30 Cubic Feet (what this guide is about)

Shell Type

Abrasion-resistant vinyl soft-shell

Water Resistance

Waterproof

Security

Combination lock

Installation

Buckle straps

Vehicle Compatibility

Trailer hitch, tow hitch, truck bed

View on Amazon: Mockins 30 cu ft Hitch Cargo Carrier Bag Affiliate link

This is a 30 cubic foot soft shell cargo bag designed for trailer hitch mounts. It measures 60 x 24 x 36 inches and weighs 20 pounds. The vinyl construction is waterproof with reinforced seams and a protective zipper flap. You get six included packing cubes for organization and a combo lock for security. It suits travelers needing high capacity without the bulk of a hard shell roof box.

Pros

• 30 cubic feet of storage capacity
• Waterproof vinyl with reinforced seams
• Includes six packing cubes
• Combo lock for security

Cons

• Soft shell offers less impact protection than hard shells
• Hitch mount blocks rear vehicle access
• No side-opening access

Good fit if

• You need maximum storage volume on a budget
• You have a trailer hitch receiver available
• You want waterproof protection for gear

Skip if

• You require a roof-mounted solution
• You need easy side access while parked
• You prefer a rigid hard shell design

Verdict: Mockins 30 CuFt Hitch Cargo Bag provides substantial 30 cubic feet of waterproof storage for hitch-mounted use. It is a practical option for hauling large loads like tents or suitcases when roof space is unavailable or inconvenient.

Specifications side by side

Frequently asked questions