How to Choose the Right Backpack Size (2023)

If you are the owner You may have noticed that many bags, like we do, are labeled in liters rather than inch-by-inch measurements. Volume or bag capacity is an important factor to consider when buying a bag. For example, a 15 liter bag is fine for everyday activities, but may not be enough for an overnight trip.

It’s incredibly hard to convey the size of the bag. Let’s compare two of my favorite backpacks: The Rains Mini 15.7 inches by 11.4 by 3.9, and the Herschel Heritage 18 inches by 12.25 by 5.5. In a side-by-side comparison, they look pretty comparable, but the Rain holds nine liters, while the Herschel holds 21.5.

So how exactly do you measure lite and what size is right for you? We spoke to bag brands to find out. Once you decide what the right liter size is for your needs, we have more recommendations than anyone could ever want. Check out our guides on the best backpacks, best messenger bags, best used bags, and best camera bags, as well as options for choosing bags and totes.

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How to calculate volume

When you think of liters, you probably think of water. While there may be brands that fill their bags with liquid and increase the size as you go, there is a more dry way to do it. According to Ahren Bohnema, product design manager at Jansport, most brands use small plastic balls (think ping pong balls).

“We fill a bag with them, zip everything up tightly, then pour the balls into a very large, graduated cylinder along the side marking lines,” says Bonema. “It looks a little primitive, but it’s incredibly accurate, and the industry standard used by most package brands.”

Because something like volume has to be universal, you hope it translates from brand to brand. “I’ve personally measured probably dozens of competitor packages, and it’s not uncommon to find things wrong,” Bonema said. Countless message boards and Reddit threads agree. Reviewers at Tree Line Review found that the claimed volume and measured volume were different. (They used pinto beans instead of balls!) JanSport wasn’t among the bags they looked at.

This is especially frustrating since most of us don’t have hundreds of pinto beans on hand. Fortunately, most of us don’t need such a precise measure of capacity. If all you need is a running bag to hold your phone, jacket and some snacks, you can comfortably imagine that an 8 to 10 liter capacity will probably do the trick. All you have to do now is to know what you want the bag for.

How many liters do I need?

what do you do If you take your bag to work and all you need to carry is a laptop, wallet, chapstick, and a notebook, look for a bag with the right size laptop pocket. I use the raincoat in this case to carry my 13-inch MacBook. But if you want a bag that can double as a diaper bag, hold a whole semester’s worth of books, or go hiking and camping, size starts to become more critical.

Bags have a great video guide comparing sizes. With that advice and our testing in mind, here’s a broad dosage guide we recommend: