Choosing the correct backpack size is important for both your physical and mental health. Carrying weight incorrectly on your back can negatively affect your spine and shoulders, causing lasting aches and pains.

A study done at Stanford reports that carrying a heavy backpack “can cause severe deterioration of the lumbar on your spine” (Hossain & Tonima). Not to mention the mental stress of constantly fiddling with unnecessary zippers and attempting to find chapstick in a Mary Poppins size bag.

This backpack size guide is geared to provide essential information in helping you find the best backpack. It will give you a simple way to determine the best possible fit based on your body’s preferences and personal style preferences.

Backpack Size Chart

Any backpack size guide should consider correct fit and backpack size for you in order to determine the best internal frame backpack for your body. Unfortunately, this involves measuring yourself. This information seems tedious but is essential in establishing what backpack dimensions  and what backpack size you need, because we are not all built for the standard backpack size.

How to Measure Your Body

1. Measure Torso Length

Measure the torso length by finding the distance between the C7 Vertebra and the the Iliac Crest. The C7 Vertebra can be found where your neck connects to your back (follow your shoulder line); the Iliac Crest can be found at the base of your hips. Use a measuring tape to obtain a vertical measurement along your spine.

2. Measure Hip Size

Wrap the measuring tape around your waist. Measure your hip size by finding the widest part of your hip, also the uppermost point of the Iliac Crest. This is your hip measurement.

Illustration from Bag Design by Fashionary

Best Backpack Size For You

Extra Small

Torso length should be less than forty centimeters and the hip measurement should be less than fifty-five centimeters.

Small

Torso length should be between forty and forty-four centimeters; and hip measurement should be between fifty-five and sixty-nine centimeters.

Medium

Torso length should be between forty-five and forty-nine centimeters; and hip measurement should be between seventy and eighty-seven centimeters.

Large

Torso length should be between fifty and fifty-two centimeters; and hip measurement should be between eighty-eight and one hundred centimeters.

Extra Large

Torso length should be greater than fifty-three centimeters; and hip measurement should be greater than one hundred and one centimeters.

How Backpack Volume is Measured

Hip and torso measurements help to identify the correct backpack size for your body type, but there is still something to consider: what will  be the use of this backpack? The answer to this question will give insight to how much volume your backpack needs.

Volume calculations for bags are done by measuring how much a bag can hold opposed to dimensions that identify what you can put in it. Volume calculations show how many liters of space available, whereas dimensions show the length and width of items that would fit. Both aspects are equally important.

The volume of a bag is calculated by measuring the available capacity including all pockets and sections of the bag. In other words, imagine filling a bag and all of its compartments with water and then measuring how much water (in liters) is poured back out.

However, if only dimensions are given, then multiplication of the dimensions will give you cubic inches, which can then be converted into liters. For example, a bag that is 24” by 16” by 9” would be 3456 cubic inches, which is 56.63 liters The intended use of the backpack determines the amount of liters needed.

Best Work Backpack Size

A good work backpack is around twenty to thirty-five liters, allowing for enough space to carry essential items like a laptop, books, office supplies, lunch tupperware,  etc. This usually has two large main compartments, a laptop sleeve, and cup holders. This is the right capacity for someone who uses a coworking space and essentially carries an office in their backpack.

Best Travel Backpack Size

Backpacks for traveling are around thirty-five to forty-five  liters. There is usually one main compartment with a laptop sleeve and at least one front pocket for easy retrieval of tickets and ID cards. This backpack needs to be large enough to fit all the essentials for traveling, while also avoiding unpleasant issues with the airlines and their policies. After all, your backpack should stay in a seat with you, not to be at the mercy of airline crews.

Best Gym Backpack Size

Gym and active backpacks are around thirty liters.There is usually one main compartment, a front pocket, and cup holders. This capacity will allow enough room for gym clothes, shoes, and some training gear.

Pocket Size Guide for your Backpack

The last essential piece of a backpack size guide looks at personal preference. After finding the best fit and size, there is one last aspect to consider: what size backpack do I need for the most essential items in my life?

Whether it may be a laptop, gym shoes, or three outfits, the final decision for a backpack size should be guided by what you deem important. Chances are if an item is deemed important enough to purchase a backpack for it, it is something that will need to be easily accessible.

Pockets accompany a backpack for this purpose and allow for customization of organization and prioritization. Below are a few helpful references for common items and the size pocket they require. Use this information to be sure that essential items are considered in the final purchase decision.

backpack size chart backpack size guide

Pens

Fourteen centimeters by three centimeters for each pen.

Name Cards

Eleven centimeters by seven centimeters.

Passport

Fourteen centimeters by eleven centimeters.

Cosmetics

Sixteen centimeters by eleven centimeters.

Sketch Book

A5 — Twenty-one centimeters by twenty-seven centimeters.

A4 — Twenty-seven centimeters by thirty-six centimeters

Mobile Phones

4.7-inch — Sixteen centimeters by nine centimeters

5.5-inch — Eighteen centimeters by sixteen centimeters

Tablets

9.7-inch — Twenty-four centimeters by eighteen centimeters.

12.9-inch — Twenty-eight centimeters by twenty-one centimeters.

Laptops

11-inch — Thirty-four centimeters by twenty-nine centimeters. 

13-inch — Thirty-eight centimeters by twenty-nine centimeters. 

15-inch — Forty-two centimeters by thirty-one centimeters.

Final Thoughts

Finding the right backpack size is all about knowing your body type and what fits your best for how you’ll use your backpack. Whether it’s work, travel, gym, or a daypack for everyday use, there’s a plethora of backpacks out there that can fit your exact use case.