How to Choose the Right Backpack: Size, Capacity & Fit
Whether you’re commuting to work, heading out for a surf session, or planning a multi-day hike, your backpack is more than just a carryall—it’s part of your daily system. Choosing the right one depends on your activity, what you need to carry, and how long you’ll be out. Let’s break it down.
Backpack Volume: Why Liters Matter
If you’ve shopped for backpacks recently, you’ve probably noticed that they’re usually sized in liters, not inches. That’s because volume capacity is a better measure of what the bag can hold.
But how do brands calculate that? Most use the same technique: they fill the pack with plastic balls (or pinto beans!), then pour those into a graduated cylinder to measure the total internal volume in liters. It may sound simple, but it’s the industry standard—and generally reliable.
📏 Important: Backpack dimensions can be misleading. Two bags with similar outer sizes can hold very different amounts depending on their design and structure.
Backpack Volume Size Guide (Liters)
Here’s a general guide to help you choose the right capacity based on your needs:
| Capacity | Best For |
|---|---|
| Under 10L | Slings & waist packs, daily essentials, running, dog walks |
| 10–19L | Compact daypacks, commuting, tablets, 13” laptops |
| 20–29L | School bags, daily work packs, 15–16” laptops |
| 30–39L | Weekend trips, gym & work combo, extra clothing |
| 40–49L | Light travel, carry-on compliant for most flights |
| 50–70L | Hiking, camping, multi-day treks |
| 70–80L+ | Extended expeditions, winter camping, gear-heavy travel |
Types of Backpacks & What to Look For
1. Everyday / Commuter Backpacks (15–35L)
Great for daily use, office commutes, or town errands.
Key Features:
- Padded shoulder straps for comfort
- Internal laptop sleeves (13–16 inch)
- Weather-resistant materials
- Multiple compartments for tech and personal items
2. Surf Backpacks (30–50L)
Designed to carry your surf gear, wetsuit, and daily items to and from the beach.
Key Features:
- Waterproof or water-resistant fabric
- Wet/dry compartments
- Fin and wax storage
- External mesh pockets
- Key clip for security
3. Travel Backpacks (25–45L)
Perfect for weekend getaways, air travel, or longer trips if you pack light.
Key Features:
- Front or clamshell openings for easy packing
- Carry-on compatible (up to 45L domestic, ~40L international)
- Ergonomic straps and back panels
- Multiple storage zones including laptop & tablet pockets
✈️ Tip: Always check airline carry-on limits. Many international carriers cap backpacks at 40L.
4. Hiking Backpacks (10–35L)
Built for day hikes, climbing, fishing or outdoor activity.
Key Features:
- Water bottle holders and hydration sleeve
- Sternum and waist straps for stability
- Durable fabric and weather resistance
- Loops for poles, tools, or helmets
🏕️ For longer hikes or overnights, size up to 40L+.
5. Camping / Trekking Backpacks (35–70L+)
These are designed for serious gear-hauling over long distances.
Key Features:
- Moulded and adjustable shoulder straps
- Load-bearing waist belt
- Large internal storage space
- Optional cooler compartments
- Rain covers and gear loops
🧭 Guide:
- 35–50L for overnight trips
- 50–60L for 2–3 days
- 65–80L+ for multi-day backcountry trips
6. Laptop & School Backpacks (10–30L)
Simple and efficient, ideal for school, work, or short commutes.
Key Features:
- Padded laptop sleeve (13–16 inch)
- USB/cable organizers
- Anti-theft features and zippers
- Lightweight and slim profile
Choosing the Right Fit
- Try it on in-store if possible, especially for larger bags.
- Adjust the straps and waist belt to shift the load properly.
- Pay attention to internal organization—some packs have better layouts than others.
- Check if your gear fits—laptop, camera, wetsuit, or extra clothing.
Final Thoughts
Liters are a helpful guide, but how the backpack feels on your body matters most. If you carry heavy loads often, invest in quality padding, strap support, and durable zippers. For lighter daily use, focus on organization and ease of access.
The perfect backpack isn’t just about size—it’s about purpose and comfort. Find the one that fits your life, and it’ll carry you everywhere you need to go.