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Why do Hiking Backpacks Say Liter?

Why do Hiking Backpacks Say Liter?

When you are shopping for a new hiking backpack, it might be confusing looking at the specifications and descriptions and reading liters. It can be hard visualizing how big a bag is when you need to figure out how big 50 liters is so you might be wondering why do hiking backpacks say liter and not another form of measurement.

Why do Hiking Backpacks Say Liter?

Understanding the size of your backpack is a key factor when you must decide on a backpack. If you choose wrong, you might end up having to leave half your gear at home.

The reason why hiking backpacks say liter is because of the standards set by authorities and manufacturers. They are dictating volume measurement for hiking backpacks to be liters.

I don’t know about you but that still sounds alien to me. How big is a backpack when it has a volume of 60 liter?

Why do Hiking Backpacks Say Liter - Cup

Different Ways of Measuring

There are different ways of measuring a backpack so let’s explore this further.

1. Measuring the Volume

In the specification section of backpacks, you must have seen that backpacks have a description of 40 liters, 50 liters, 75 liters and more. This indicates the volume of the backpack and how much storage space is available in the backpack (including the pockets).

So how do you determine the storage space? First you determine the volume of a backpack and for that manufacturers fill the backpack with water.

Water can go into any space and take on any form. The amount of water used to fill the whole backpack is the volume of the backpack.

Each compartment can be measured separately as well giving you an indication of the separate pocket space.

To get the overall volume of the backpack, they add together all the measurements of the external and internal pockets, as well as the inside space. This gives you a better idea of the full volume of the backpack.

2. Measuring the Dimensions

If you like maths, like most people do (not), you can also measure the dimensions of the backpack with a ruler or measuring tape. To do this, you will need to measure the length, width and height in centimeters.

If you have extra time, you can also measure the internal dimensions of the backpack.

Once you have the dimensions of length, width and height, you can multiply them and divide by 1000 to get a rough idea of the volume.

Personally, I have never gone through all of this trouble but knowing the length, width and height is handy when you need to travel and know your backpack needs to fit into smaller spaces.

Why do Hiking Backpacks Say Liter - Measuring Tape

Standard Sizes

When you understand the different volumes and sizes, you can generalize how large the backpacks of a specific volume are. It is not 100% accurate but will give a good estimation.

  • 8 L backpack: 17” x 8” x 5”
  • 25 L backpack: 21” x 11” x 6.5”
  • 30 L backpack: 21″ x13.5″ x 9.5″
  • 40 L backpack: 21” x 14” x 9”
  • 50 L backpack: 29.5″ x 13″ x 10″
  • 70 L backpack: 28″ x 14″ x 12″
  • 110 L backpack: ‎30” x 18.5” x 12.5”

Remember that you shouldn’t choose a backpack only based on the volume. You also need to take into consideration what size you are and the length of your back. You need to ensure the backpack fits comfortably on your body.

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What Size Do You Need?

Now a big 75 liter backpack might fit comfortably on your body but do you need that for a 3 hour hike? Probably not, so let’s look at the most common sizes and uses for backpacks.


For shorter trips you can look at backpacks in the rage of 8 – 25 liter. You will only carry a few essentials and don’t need a big backpack.

Overnight Backpacks

When you go on an overnight trip, you need to carry a tent and sleeping bag and more essentials. A bigger backpack is needed and the ideal backpacks for this trip range from 30 – 50 liters.

Why do Hiking Backpacks Say Liter - Backpack

Weekend Backpacks

Fancy more than one night out? Look at backpacks ranging from 30 – 70 liters to carry the extra goods and gear.

Multi-day Backpacks

If you are ready to pack the house and leave for a while, you will need a backpack with sufficient space for a long journey. For multi-day backpacks a volume of 50 – 110 liters will have the space you need.  


Using liters as measurement is a rising standard in the backpack world and won’t go away any time soon. The more you explore different backpacks, the quicker you will be able to visualize how big the compartment space is based on the volume.

Thank you for reading this article and I hope this helps you in choosing your next backpack. Enjoy your hiking while building a stronger life.

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