How to Measure Backpack Dimensions

By Thomas Sorheim •  Updated: 05/03/20 •  5 min read
A girl standing with the backpack

Nearly everyone has owned or will own a backpack at some point in their life. Whether your first backpack was bought when you started school or for some other purpose, just about everyone knows how useful they can be for carrying your personal belongings.

However, despite the fact that most of us have been using them for years, it’s surprisingly common for a lot of people to have no idea how to properly measure backpack dimensions.

Perhaps the main reason for that backpacks aren’t usually measured how you might initially think (height by length by width).

Rather, they are measured by their available capacity in liters.

Anyone can figure out the precise dimension measurements in inches of a backpack using a measuring tape.

However, in this article, we’ll not only explain how to do that properly, but we’ll also aim to give you a better understanding of the more commonly used measurements (volume).

Measuring Backpack Dimensions vs Volume

Backpack and hiking shoes next to the lake and mountains

The dimensions of a backpack are easy enough to understand. Simply use some measuring tape, and measure the height, length, and width of your bag. For example, a standard 40L hiking backpack could have dimensions like this: 21.3” x 12.6” x 8.3”.

On the other hand, the volume of a backpack refers to just how much carrying capacity it has. Hiking backpacks can range from having a 25L capacity all the way up to over 50L. The volume will largely depend on the size of the bag, and whether it’s intended for simple day trips or long, multi-day hikes.

So how is a hiking backpack volume determined? Good question! You can get a (very) rough estimate of the volume by calculating the dimensions, although, for obvious reasons, this isn’t always accurate.

More commonly, backpack manufacturers will measure the volume of their backpacks by adding up the total volume of storage on the bag, such as the main compartment and any additional side or front pockets that can be zippered shut or closed in some other way.

These measurements are taken in cubic inches and then converted into liters to provide the final volume (e.g. 40L).

Further complicating matters is that some other manufacturers will also include side pouches meant for holding bottles or cameras in their measurements.

Since the method and measurements that are used to figure out backpack volume can vary from manufacturer to manufacturer, if you are in doubt, we recommend to simply contact the maker of your bag to find out their exact measuring criteria.

A person holding brown backpack

How to Choose the Ideal Sized Backpack

When choosing the right hiking backpack for you, there’s a few basic guidelines that you are going to want to keep in mind. For some people, they can get by with one single backpack that matches their needs perfectly. On the other hand, some people may want to look into getting two or even three different sized backpacks to use for their hiking expeditions. 

Types of Packs

Depending on the type of hiking excursion that you are planning, there’s several different types of packs available. Daypacks, as the name suggests, are suitable for hikes that won’t take any longer than a day.

There’s also hiking backpacks made specifically for overnight trips, weekend trips, and multi-day (3-5 days) trips. As you can imagine, each type of backpack will have a different volume. 

Your Size

Another factor to consider when choosing what backpack size to go with is your own size, strength, and endurance levels. You should measure your torso, which will help you figure out the ideal length your backpack should be. Your backpack should be of equal or lesser length than your measurements. 

What You Will Be Packing

The final big consideration is just what exactly you will be packing for your trips. If you’ll only be taking the basic essentials, you can make due with less volume. On the other hand, if you’re someone who likes to bring along plenty of extras, then you should definitely look into larger sized packs.


At first glance, measuring backpack dimensions can seem more than a little confusing. Hopefully after reading this article, you have a much better understanding of what to look for when choosing a backpack and how to measure it.

As long as you keep in mind the three key points that we discussed above (your torso measurement, how much space you’ll need for your items, and what types of hikes you will be going on), you’ll easily be able to measure both the dimensions and volume of a hiking backpack to find one that best suits your needs.

The reason this is all so important is that if you’re going to be spending several hours at a time carrying a backpack full of equipment, then you are absolutely going to want to be sure your bag is sized properly and that it is a comfortable fit.

A properly sized backpack can make all of the difference between an immensely enjoyable hike or a completely miserable experience.

Thomas Sorheim