Typical volume requirements
Pack requirements vary hugely depending on your hiking style, the weather, and on the length and purpose of your trip. But to get you oriented, here are some typical volumes:
For a summer day-pack 15 liters should be adequate.
Lightweight hikers might tackle a thru-hike with a 40-50 liter pack.
Traditionalist hunters, fishers and bushcrafters packing into a base camp
might need 100 litres or even more, depending on their style and
While camping in extreme cold requires more volume for bulky sleeping
bags and clothing.
Most people will simply list their equipment and total up the estimated volume of each item. Then add around 1.5 litres for each day of food, and, obviously, 1 liter for each liter of water.
How to select your pack
Unless you intend to build up a quiver of packs for different uses, the key is to err on the large side. Most of the pack's weight is in the frame and straps - the weight of additional fabric for an extra 10 or or 20 liters of capacity is minimal. If the pack has a good compression system you can use it for a very wide range of capacities and still have it carry well. It's also quicker and easier to pack a sack when it's not too tight for capacity. There's very little penalty for a pack that's a bit larger than you need, while a pack that's too small can be a major issue.
Packs will generally fall into 3 categories:
- Frameless sacks for light loads
- Packs with a lightweight frame designed for loads up to around 15kg/30lbs
- Load haulers with substantial suspensions designed for big weights.
At the very most you should be able to cover your general requirements with 1 pack in each class. Though for many people, a single pack with a lightweight frame should cover all their needs.
Finally, there is no standard for measuring pack volume so advertised capacity can vary widely between manufacturers. Again, the answer is to err on the large side. Something I've done in the past is to take my equipment into the store and see how it fits in the pack - a good specialised retailer should be happy accommodate you, particularly if you call ahead and ask.