What Size Rooftop Cargo Box Do I Need? Now You Know!

Whether you’re using a rooftop cargo box for camping, winter sports, traveling, or just for additional storage, choosing the right size for both your vehicle and goods is incredibly important. Because all vehicles are different sizes and allow various rooftop weights, it’s hard to determine which box is best suited for your situation. Therefore, what size rooftop cargo box do you need?

The size of your rooftop cargo box will vary on a bunch of different factors. However, the primary ones you’ll want to consider are your vehicle’s hatch clearance, gross rooftop weight capacity, and, ideally, what type of goods will be transported.

Because of the sheer number of vehicles and cargo box variations people can buy, it’s tough to decipher what sized box every individual needs. However, there are ways in which you can simplify this. To find out this information, we recommend becoming knowledgeable on the below cargo box-sizing guide:

How to purchase the correct sized cargo box

Above, we mentioned that there isn’t a specific size that “fits all” in cargo boxes. Because of this, you’ll need to use some of your own initiative. Without a doubt, performing the below accurately will hugely reduce the chances of you purchasing the wrong-sized cargo box. They can become exceptionally expensive, and the shipping follows suit also. Therefore, to reduce the occurrence of you having to pay return shipping, become familiar with the below.  

Decide what cargo box will fit your vehicle

Before finding out the below information, you’ll want to decide which cargo boxes actually fit your car. There are a few factors you’ll want to consider, weight, length, and width. Here’s why:

Weight – First, become knowledgeable on your vehicle’s rooftop maximum capacity. Afterward, you’ll want to find a box that suits the criteria based on your findings. You’ll want to calculate the total weight of your roof rails (if not already installed), crossbars, cargo box, and additionally, the goods you’ll transport. When you have this information, you can start eliminating some cargo boxes available on the market.

Length – Including the above, you’ll want to decide on an overall length for your cargo box. Here you’ll want to consider the total length of goods you’ll transport, along with the overhang on both the rear and front. Overhang on the rear of your vehicle could prevent the usage of your boot. Therefore, ensuring it doesn’t affect its access is vital. When it comes to the front of the car, you’ll want to think about the overall aerodynamics and visibility. If you’re having visibility issues from a cargo box, it’s way too big. Because of this, ensure it doesn’t overhang your front windscreen much.

if you're looking for something large I’d recommend making yourself some coffee and checking out this article for more.

Width – Unlike the above, the width needs to be considered with your crossbars. To install a cargo box, you must attach it to your roof. Because of this, you’ll want to develop knowledge on the maximum installation width for your crossbars.

Think about what you’ll store in your cargo box

Now you’ve identified the above, you’ll want to really start considering what you’re going to transport within your cargo box. Whether you’re transporting ski equipment, camping accessories, or tools, the total size of the cargo box will vary. Because of this, we’ve provided a “gear capacity” table below. The total number of cubic feet, inches, and liters is recommended depending on how many people are traveling with you.

Number of people





Gear capacity

12 cu. ft. / 20,736 cu. in. / 340 liters

15 cu. ft. / 25,920 cu. in. / 425 liters

18 cu. ft. / 31,104 cu. in. / 510 liters

21 cu. ft. / 36,288 cu. in. / 595 liters

Please note that the above are rough estimates. However, it provides reasonable estimates to visualize how much potential room you might need within your cargo box.  

Don’t forget other cargo carriers

After becoming knowledgeable on the above, you can start developing a better understanding of what cargo box size you might need. That being said, if you’ve discovered that a cargo box might not be suitable. You may want to become familiar with other cargo carriers. Below, we briefly mention the different available types to obtain a more personalized storage device for your situation.

  • Baskets – Cargo boxes are excellent, but you’ll be restricted on space. However, this isn’t a problem with a basket (or also known as a tray). These cargo carriers require you to strap goods onto an open basket for transportation. Although you lose waterproofness because your goods will be open to the natural environment, you can travel with much taller or longer equipment.
  • Bags – The closes cargo carrier to a box is a bag. Bags are great; they look good, are waterproof, and don’t require you to be a genius to install. Usually, they’re the smallest type of cargo carrier. Therefore, if you’ve noticed that rooftop boxes are too big for your application, this might be your best option.
  • Sport-specific – If you’re purchasing a rooftop box to transport one particular style of equipment, it might be more beneficial to purchase something suited to its needs—for instance, these ski-specific rooftop cargo carriers.

By knowing what’s available on the market, you can purchase something that’s much more suited to your requirements. After all, that’s the end objective, right?


After reading the above, you should now understand how to reveal the perfect cargo box size suitable for your needs and vehicle. Making sure you get this correct the first time is significant. Failing could result in you having to return your box via mail. If that occurs, the shipment can cost a substantial amount of money because of its sheer size.

Additionally to the above, you might want to consider the style and material of a cargo box. The last thing you’ll want is your vehicle to lose its aesthetics or your box breaking after a few road trips. If you’re going to use a cargo box year-round or for a few months each year, it’s undoubtedly worth investing in something more worthwhile than the cheaper models on the market.

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