Backpacks come in all shapes and sizes, and the numbers on the label, like 20L or 40L, don't always mean much at first glance. Choosing the right size makes your bag more comfortable, easier to carry, and better suited to how you actually use it. Here's a simple guide by use.
What Backpack Size Means
Backpack capacity is usually measured in liters (L), which tells you how much space is inside. A bigger number means more room, but also a larger, heavier bag. The goal is to choose enough space for your needs without carrying extra bulk.
Common Backpack Sizes by Use
Small (under 15L): Quick outings
Great for errands, short walks, and carrying just the essentials like a phone, wallet, keys, and water. Slings are a handy alternative, like the WATERFLY Crossbody Sling Backpack.
Medium (15 to 30L): Everyday, school, and work
The most popular size. It fits a laptop, notebooks, lunch, and a light jacket. The Shrrie 15.6" Business Laptop Backpack is a solid daily pick.
Large (30 to 45L): Carry-on travel
Ideal for weekend trips or one-bag travel. Many airlines accept bags around 40L as carry-ons. See the 40L Flight Approved Carry-On Backpack or the mixi 18 Inch Carry-On Travel Backpack.
Extra large (45L+): Long trips and heavy gear
Best for extended travel, gaming setups, or bulky gear. The Extra Large 18.4" Travel Laptop Backpack holds plenty.
Kids and toddlers
Little ones need small, light bags that fit their frame, like the mommore Toddler Backpack.
How to Choose the Right Size
1. List what you carry daily
Lay out your usual items. If they fit into a medium bag with room to spare, don't go bigger.
2. Match your torso length
A backpack should sit between your shoulders and the top of your hips. Too long or too short will feel uncomfortable.
3. Check airline limits for travel
If flying, compare the backpack's dimensions with your airline's carry-on and personal item rules.
4. Look for comfort features
Padded straps, a breathable back panel, and a chest strap help with heavier loads.
Tips and Mistakes to Avoid
- Don't buy a bag much bigger than needed. You'll fill it and carry extra weight.
- Keep your loaded backpack under about 10 to 15% of your body weight for daily use.
- Put heavy items close to your back for better balance.
- Use both straps to prevent shoulder strain.
Shop the Collection
Explore Ttavello's Backpacks collection for everyday, laptop, travel, and kids' backpacks in every size.
Related Guides
Read next: How to Choose a Laptop Bag for Work, School, and Travel, Backpack vs. Duffel Bag: Which Is Better for Travel?, and Carry-On Size Guide: What Travelers Should Know Before Flying.