How Much Empty Space In Backpacking Backpack?

How Much Empty Space In Backpacking Backpack? Size Capacity Suggested Uses Mini and Small Backpacks 6 -10 Litres Days Out / Kids Bags / Sports Daypacks 10 – 30 Litres Commuting / Hiking / Day Walks Medium Backpacks30 – 50 Litres Overnight Trips / Camping / Hiking Large Rucksacks 50 Litres + Travelling / Backpacking