Backpacks are probably one of those things that many people don’t bother measuring. However, getting the wrong size backpack, as well as several other factors, may lead to neck and shoulder pain. For that reason, it’s generally a good idea to choose a backpack size that matches your size and needs.
The standard everyday backpack typically measures 22 × 14 × 9 inches (55.9 × 35.6 × 22.9 centimeters), give or take a few inches. They are designed to carry around 15 to 35 liters (4 to 9.2 gallons) of supplies at a time. However, the actual dimensions of a backpack will typically depend on what kind of backpack it is and how much stuff it can store at once.
For the remainder of this guide, I will briefly cover the various kinds of backpacks, their size dimensions, and other factors that you should consider when shopping for a backpack.
Backpack Types Based on Uses and Carrying Capacity
There are 2 ways we can categorize backpacks—by their uses and by their carrying capacities. I’ll cover both categorizing methods below.
Backpacks by Uses
When categorizing backpacks by how they’re intended to be used, they generally fall into one of 4 categories: hydration, everyday, hiking, and laptop or school, with the best backpack being the one that suits your needs the best.
Hydration backpacks are the smallest type of outdoor bag that is immediately identifiable by a pouch or bladder used to store liquids. Some of the smaller hydration backpacks are designed to carry as little as 7 liters (1.8 gallons) of supplies at once, while larger ones have more than double the carrying capacity (20 liters or about 3.6 gallons). Before being filled with liquid, a small-sized hydration backpack will measure around 11 × 10 × 4 inches (27.9 × 25.4 × 10.2 centimeters).
Everyday backpacks are backpacks that you can use for anything, including hiking and storing school supplies. They typically hold between 15 to 35 liters (4 to 9.2 gallons) of supplies at a time, and they have soft cushioning and internal pockets to store large laptops, textbooks, and stationery. The average size of a standard everyday backpack will typically measure 22 x 14 × 9 inches (55.9 × 35.6 × 22.9 centimeters).
Hiking backpacks are made for those that need to carry large supplies during outdoor excursions. They generally have waterproof exteriors, which will keep your supplies dry at all times. Hiking backpacks range from 20 to 60 liters (5.3 to 15.9 gallons) of supplies at once, though some hiking bags can be even larger. Depending on the capacity of the hiking bag, it can be as small as 17 × 8 × 5 inches (43.2 × 20.3 × 12.7 centimeters) or as large as 30 × 18.5 × 12.5 inches (76.2 × 47 × 31.8 centimeters) when empty. They will usually come with additional sleeves, compartments or pockets that serve as a water bottle holder.
A laptop backpack is a type of backpack that has a dedicated compartment or sleeve for carrying laptops within its main compartment. A daypack, suitable for carrying a laptop and a few other essentials, is typically under 14 liters or 2,500 cubic inches. This type of backpack usually doubles as a school backpack.
Backpacks by Capacity
When looking exclusively at backpacks for outdoor activities, you will generally want to know the volume of thebag or the backpack capacity. For that reason, we can categorize backpacks by their carrying capacities. The 3 main categories are weekend, multiday, and extended-trip backpacks. Weekend backpacks are highly efficient, ultra-lightweight bags that can be used for carrying supplies for up to 3 nights. They generally hold up between 30 and 50 liters (7.9 and 13.2 gallons). Many 40-liter weekend backpacks measure 21 × 11 × 8 inches (53.3 × 27.9 × 20.3 centimeters).
Multiday backpacks are bags large-sized outdoor bags that carry between 50 and 80 liters (13.2 and 21.1 gallons) of supplies at any given time. These backpacks are ideal for outdoor trips lasting between 3 and 5 nights. If you shop for a 65-liter backpack, it’ll measure around 27 × 16 × 9 inches (68.6 × 40.6 × 22.9 centimeters). This size and smaller will usually work as carry-on since they meet airline size restrictions.
Extended-trip backpacks are oversized backpacks that can carry as many supplies as you need for a trip that lasts over 5 nights. They can carry as little as 70 liters (18.5 gallons) of clothing and cooking utensils, but some bags go over the 100-liter (26.4 gallons) figure, which is plenty of space for your personal items. They will contain various compartments on the sides and near the bottom of the bag, but on average, a 100-liter bag will measure somewhere around 18 × 13 × 9 inches (45.7 × 33 × 22.9 centimeters).
Bag Size Chart
You can use the following table as a reference for knowing backpack sizes based on their types.
| Backpack Types | Dimensions (H × W × D) | Capacity | |
| By Uses | Hydration | 11 × 10 × 4 inches 27.9 × 25.4 × 10.2 centimeters | 20 liters 3.6 gallons |
| Everyday | 17 × 8 × 5 inches 43.2 × 20.3 × 12.7 centimeters | 15 to 35 liters 4 to 9.2 gallons | |
| Hiking | 30 × 18.5 × 12.5 inches 76.2 × 47 × 31.8 centimeters | 20 to 60 liters 5.3 to 15.9 gallons | |
| By Capacity | Weekend | 21 × 11 × 8 inches 53.3 × 27.9 × 20.3 centimeters | 30 and 50 liters 7.9 and 13.2 gallons |
| Multiday | 27 × 16 × 9 inches 68.6 × 40.6 × 22.9 centimeters | 50 and 80 liters 13.2 and 21.1 gallons | |
| Extended-Trip | 18 × 13 × 9 inches 45.7 × 33 × 22.9 centimeters | 70 to over 100 liters 18.5 to over 26.4 gallons | |
Available Features in Backpacks
When shopping for a backpack, you will come across a wide assortment of features. I’ll go over some of the more important ones down below.
Frame
A backpack’s frame refers to the solid panels built into or around a backpack to give it structure. There are 3 types of frames to choose from—internal, external, and frameless. Frameless backpacks may come with detachable frames to increase storage capacity and reduce weight.
Ventilation
Ventilation refers to how much air can pass through a backpack. A poorly ventilated backpack may induce back sweat, which can make hiking intolerably uncomfortable. Some backpacks have built-in “chimneys” that force air toward your back to solve ventilation problems.
Pockets
A backpack’s pockets refer to the small compartments that are stitched onto the sides or near the bottom of the backpack’s base. The more pockets there are, the more small-sized items you can keep separate from large-sized camping supplies. Ideally, the backpack will have side pockets for carrying water bottles and other small items.
Compartments
Compartments are individual storage spaces in and around backpacks with zippers. They are used mainly for organizational purposes.
Interior Padding
The thicker the padding, the less prone delicate electronics, such as laptops or smartphones, will become damaged when placing your backpack on the ground. You should also look at the padding on the straps to ensure that they don’t dig too deep into your shoulders when the backpack is full.
Shoulder Straps
The shape and style of straps can impact weight distribution and reduce rubs during use. It is crucial to wear both straps to distribute the weight and adjust them for an ergonomic fit.
FAQs
1. Can you use a backpack as a suitcase when you’re flying?
Yes, you can use a backpack as a suitcase or a piece of luggage when flying, but it depends on the size and weight of the backpack and the airline’s regulations. Some airlines allow backpacks as carry-on and personal items, while others may consider them as checked luggage.
If you’re using a carry-on backpack, you don’t have to check it into your flight, but it will have to meet strict size restrictions to ensure that it fits underneath your seat, fits underneath the seat in front, or fits inside the overhead bin.
2. Can a backpack hold more gear than the advertised volume?
Yes, they can. It ultimately depends on the dimensions of the bag and how elastic its material is. Smaller backpacks of 30-liters, for instance, can sometimes hold around 31 or even 32 liters but will not hold anywhere near as much as a backpack of 40 liters. It’s generally a good idea to measure a backpack and compare it to the number and sizes of the items you wish to take with you.
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