Backpack Size Guide: How Big Are 15 to 60 Liter Backpacks

When buying a backpack there are so many things that you need to check and the backpack size is one of them. You need to choose the right backpack size for yourself so you can use it for the purpose you want.

This is why it is important for you to know how big is a backpack and what you can use it for.

So, in this backpack size guide, we are going to cover how big are the backpacks based on the size.

So, let’s get started.

How Big is a Backpack?

The size of the backpack depends on the exterior measurement of the dimension of the backpack. You can easily measure the exterior dimension of the backpack using a measuring tape or a ruler which can give you an idea of how big is your backpack.

But, as you know that you are going to keep your stuff inside the backpack and this is why it is more important for you to know the interior dimensions of the backpack.

If you know the right size of the interior dimensions of the backpack then you can easily keep your gears and belongings in it.

  • To do so, you can use the measuring tape and start measuring the main compartment of the backpack first so that you can understand approximately how big the backpack is.
  • Next, you should measure the exterior dimensions of the backpack to get a clear idea of how it is going to fit you.

Why Measure the Exterior Dimensions Of The Backpack?

Although, measuring the internal dimension is going to help you to understand what you can keep in it.

But, it is not so easy to measure the interior dimension because you can not easily make a backpack inside out and especially when it is built with quality material to resist water.

This is why measuring the exterior dimension can give you a good and easy understanding of the backpack size because the dimension mentioned on the website and manufacturer pages is the exterior dimension of the backpack. 

The reason behind measuring the exterior dimension of the backpack is to help the buyer to understand how it is going to fit them after they purchase it.

Now, you must be thinking what’s about the storage capacity of the backpack, how you are going to know what you can keep in it if you do not know the interior dimensions. Right?

So, let’ me tell you that the storage capacity of the backpack can be measured using some other methods instead of measuring the internal dimensions of the backpack which I have discussed in one of my previous articles about why backpacks are measured in liters.

I highly recommend you read this so you can understand how you can measure the exact capacity of the backpack at home.

Backpack Size Guide Table

SizeDimensionsCapacity (cubic inches)
15 Liter Backpack18.4 x 11.2 x 1.6 inches915.356
18 Liter Backpack 9.06 x 6.69 x 16.54 inches1098.43
20 Liter Backpack 19 x 13 x 1.5 inches 1220.47
21 Liter Backpack17.5 x 11 x 5.5 inches1281.5
25 Liter Backpack 17.56 x 12.05 x 4.76 inches1525.59
30 Liter Backpack 18.11 x 10.63 x 11.81 inches 1830.71
35 Liter Backpack 19.5 x 11.5 x 5.9 inches2135.83
40 Liter Backpack 20.5 x 13 x 7.1 inches 2440.95
45 Liter Backpack 21.7*12.9*9.8 inches2746.07
50 Liter Backpack25 x 13 x 12 inches3356.31
55 Liter backpack26 x 14.25 x 4.5 inches3661.42
60 Liter backpack 26.77 x 13 x 7.87 inches3661.42

Backpack Volume Explained

The volume of the backpack is the best option to understand how many items you can carry with you and what should be the size of those items.

Generally, the volume of the backpack is measured using the dimensional method and later it is converted in liters from the cubic inches to make it more related and to follow the standards.
To keep things as simple as possible, the backpacks are divided into three categories.

  • Small Sized Backpacks (Under 20 Liter)
  • Medium Sized Backpacks (Between 20 to 40 liters)
  • Large Sized Backpacks (Above 40 Liters)

In this guide, we will cover only those backpacks that are up to 40 liters of capacity because the backpack up to this capacity is too large and they are designed for some specific things like hiking or camping or something similar.

If you are looking for a hiking backpack then backpacks above 35 liters are really a great choice for you but in case you are looking for a backpack for daily use then a backpack under 35 liter of capacity is going to be the right choice. 

#1. Small Sized Backpacks (Under 20 Liters)

Backpacks under 20-liter capacity are good for those who carry few items in the backpack and do not want to load their shoulder with a lot of stuff.

In a 20 liter backpack, you can easily keep your sunglasses, water bottle, keys, two to three books, and laptop if a laptop sleeve is available. 

This means a 20-liter backpack is enough big to hold all of the items that you will require whenever you travel to nearby stores, tuition classes, or just for roaming around the streets.

#2. Medium Sized Backpacks (Between 20 to 40 liters)

Medium-sized backpacks are quite common for weekend travels. You carry enough items inside the medium-sized backpack that you will need during your weekend travel. Also, medium-sized backpacks are quite common among the students to carry the study material.

These backpacks are designed in such a way that you can carry all your accessories easily without feeling the load on your shoulder.

#3. Large Sized Backpacks (Above 40 Liters)

Large-sized backpacks are designed especially for hikers, campers, and sometimes for backpackers who are about to backpack for a long time. 

This backpack allows you to carry as many as possible items and gear with you so you do not have to carry two or three different backpacks during your hike.

Also, keeping in mind all the needs of the hiker the backpack is designed in such a way that you can carry the tent by attaching it to the backpack, sleeping bags, and cooking utensils with you during your hike in the most effective way.

Drawback Of Carrying Backpack Under 15 Liters

The backpack is made to carry important accessories and it is always beneficial if you are able to carry all the items that you require everywhere. 

In the case of the backpacks that are less than 15 liters of capacity, there is a storage problem. You can not carry everything with you easily, you will have to manage and leave out many necessary items on the table even if you want to carry it with yourself. 

Also, there are very few brands that provide a laptop sleeve under the 15-liter backpack. So, you will not be able to carry the laptop with you which is again a problem. 

This is why I will advise you to have a backpack that is at least above 15 liters of capacity.


How Big is a 15 Liter Backpack?

18.4 x 11.2 x 1.6 inches is the average dimension of the 15-liter backpack which has a capacity of 915.356 cubics inches. The 15-liter backpack is generally considered a small-sized backpack that generally weighs approximately 1.1 pounds.

You can keep the following items in the 15-liter backpack.

  • Small Book
  • Sweater or Jacket
  • Headphone
  • 13 icnhes laptop
  • Pair of Jeans
  • Water Bottle

How Big is an 18 Liter Backpack?

9.06 x 6.69 x 16.54 inches is the average dimension of the 18-liter backpack which has a capacity of 1098.43 cubic inches. The 18-liter backpack is generally considered as a small-sized backpack that weighs a1.8 pounds. 

You can keep the following items in the 18 liter backpack.

  • Small Book
  • Water Bottle
  • Two 1 Inch Binders
  • Sweater or Jacket
  • Large headphone
  • 13 icnhes laptop
  • Pair of Jeans

How Big is a 21 Liter Backpack?

17.5 x 11 x 5.5 inches is the average dimension of the 21-liter backpack which has a capacity of 1281.5 cubic inches. The 21-liter backpack is generally considered a medium-sized backpack whose weight ranges between 1.75 pounds to 1.90 pounds. 

You can keep the following items in the 21 liter backpack.

  • Small Book
  • Two Sweaters or Jackets
  • Large headphone
  • 15 icnhes laptop
  • Pair of Jeans
  • Water Bottle
  • Two 1 Inche Binders.

How Big is a 25 Liter Backpack?

17.56 x 12.05 x 4.76 inches is the average dimension of the 25-liter backpack which has a capacity of 1525.59 cubic inches. The 25-liter backpack is generally considered a medium-sized backpack whose weight ranges between 1.75 to 2 pounds. 

You can keep the following items in the 25 liter backpack.

  • Sweater or Jacket
  • Large headphone
  • 15 icnhes laptop
  • Pair of Jeans
  • Medium Sized Book
  • Water Bottle
  • DSLR camera Insert
  • Two 1 Inch Binders.

How Big is a 35 Liter Backpack?

19.5 x 11.5 x 5.9 inches is the average dimension of the 35-liter backpack which has a capacity of 2135.83 cubic inches. The 21-liter backpack is generally considered a medium-sized backpack whose weight ranges between 1.75 pounds to 1.90 pounds. 

You can keep the following items in the 35 liter backpack.

  • Large headphone
  • 15 icnhes laptop
  • Pair of Jeans
  • Pair of Shoes
  • Large Text Books
  • Medium Sized Books
  • Water Bottle
  • Sweater or Jacket
  • DSLR camera Insert
  • Two 1 Inch Binders.

How Big is a 45 Liter Backpack?

21.7*12.9*9.8 inches is the average dimension of the 45-liter backpack which has a capacity of 2746.07 cubic inches. The 45-liter backpack is generally considered a large-sized backpack which weight of the backpack generally ranges between 2.1 pounds to 2.3 Pounds. 


How Big is a 50 Liter Backpack?

25 x 13 x 12 inches is the average dimension of the 50-liter backpack which has a capacity of 3356.31 cubic inches. The 50-liter backpack is generally considered as a large-sized backpack which weight of the backpack generally ranges between 2.4  to 2.7 pounds.


How Big is a 55 Liter Backpack?

26 x 14.25 x 4.5 inches is the average dimension of the 55-liter backpack which has a capacity of 3661.42 cubic inches. The 60-liter backpack is considered a large-sized backpack where the weight of the backpack ranges between 2.4 Pounds to 2.7 pounds.


How Big is a 60 Liter Backpack?

26.77 x 13 x 7.87 inches is the average dimension of the 60-liter backpack which has a capacity of 3661.42 cubic inches. The 60-liter backpack is considered a large-sized backpack where the weight of the backpack ranges between 2.4 Pounds to 2.7 pounds. 


I have not mentioned much about what you can keep in the backpack that is above 35 liters of the capacity because it depends on how well you are in organizing the backpack and what type of features your backpack provides. 

Backpack over 35 liters of capacity has a lot of space and provide some extra belts/straps that can be used to attach different types of items, you can use the bungee cords on the backpack to attach the utensils that you will need on your hike or you can attach the sleeping bag to the backpack using the straps and buckles. 

Conclusion

In conclusion, in the backpack size guide, we came to know that the backpack size is measured by measuring the external dimensions of the backpack. 

And you should choose the right size of the backpack so that it can fit perfectly on your back and do not cause you back pain and other problems.

However, the capacity of the backpack is a little different from the size of the backpack because many backpacks provide extra features, pockets, and special compartments of the same size which makes the real difference in the capacity of the same sized backpack.