One of the most common questions we hear is: what size backpack do I need? The answer depends on how you plan to use it. A 20-litre daypack and a 50-litre travel pack serve completely different purposes, and choosing the wrong size means either carrying too much or running out of space. In this guide, we break down backpack sizes by activity so you can pick the perfect fit.
Backpack Sizes Explained (Litres)
Backpack capacity is measured in litres (L). Here is a quick overview of the main size categories:
- 10-20L (Sling bags and small daypacks): Phone, wallet, keys, a water bottle, and a light jacket. Perfect for city walks and short outings.
- 20-30L (Daypacks): Laptop, lunch, gym clothes, books. Ideal for daily commutes and work.
- 30-40L (Multi-day packs): Enough for 2-3 days of clothing and gear. Great for weekend trips.
- 40-50L (Travel backpacks): A week or more of clothes, carry-on friendly on most airlines. The go-to for travel.
- 50L+ (Expedition packs): Long hikes and camping with heavy gear. Too large for daily use.
What Size Backpack for Daily Commute?
For a daily commute, choose a 20-30 litre backpack. It should hold a 15-16 inch laptop in a padded compartment, plus room for lunch, a water bottle, and a light jacket. A large capacity backpack in the 25-30L range is ideal if you also carry gym clothes or documents. Look for a design with multiple compartments so everything has a place.
What Size Backpack for Travel?
For travel, a 40-50 litre travel backpack is the sweet spot. It fits a week of clothing while staying within most airlines’ carry-on limits. If you prefer to pack light, a 35L pack works; if you need room for shoes and electronics, go closer to 50L. A travel backpack with shoe compartment helps you organise dirty shoes without sacrificing main space.
What Size Backpack for Hiking?
For day hikes, 20-30L is plenty for water, snacks, layers, and a first-aid kit. For overnight hikes, choose 30-50L depending on whether you carry a tent and sleeping bag. Fit matters more than size: the pack should sit comfortably on your hips and shoulders.
How to Check If a Backpack Fits
A properly fitted backpack should sit high on your hips, with the shoulder straps snug but not tight. There should be no gap between the pack and your back, and the weight should rest mainly on your hips for packs over 30L. If possible, load the bag with weight and walk around before buying.
Final Size Recommendations
- Day trip or commute: 20-30L
- Weekend getaway: 30-40L
- Week-long travel: 40-50L
- Overnight hike: 30-50L
Still unsure? Start with a versatile expandable travel backpack that works for both daily commutes and short trips. Check out our expandable waterproof travel backpack — one bag that adapts to almost any size need.