What Backpack Capacity to Choose: 30L, 40L, or 50L

Una of the questions I get asked most in the shop is: “What pack capacity do I need?”

The doubt is usually the same: 30L, 40L, 50L or more? And many times the answer doesn’t depend on how many days you’re out, but on the real volume of your kit and how you use it.

What really matters is the volume of your gear (and how much buffer you need for food, water, and weather changes).

In this guide you’ll see when a 30L, 40L, 50L, or 60L+ pack makes the most sense, with a practical, realistic approach for hiking (and especially useful if you want to go lighter).

The key rule

Trip length doesn’t determine your pack. What actually takes up space is:

• Sleeping bag (often the bulkiest item)
• Sleeping pad
• Shelter (tarp or tent)
• Clothing (especially in cold conditions or variable weather)
• Food
• Water (depending on the route)

That’s why you can do long routes with 40–50L packs if your gear is compact.

And the other way around: you might need 50–60L for just a few days if you’re carrying a bulky bag or winter kit.

30-liter packs

Who they’re for

• Day hikes
• Fast-and-light trips.
• Minimalists with ultralight, compact gear
• Mild, stable climates

When to choose 30L

• You carry only the essentials and your kit packs down small
• You don’t need bulky extra layers
• You don’t usually carry much water or food

Typical limitation: very little buffer for weather shifts, multi-day food, or bulky items.

40-liter packs

For many hikers, 40–45L is the sweet spot for ultralight backpacking.

Enough capacity for multi-day trips without hauling “empty” liters.

Who they’re for

• Multi-day trips
• Long-distance hiking with compact gear
• Typical 3-season use

When to choose 40L

• Your kit is well optimized (or you’re getting there)
• Your sleeping bag and pad aren’t especially bulky
• You hike routes with fairly frequent resupplies

50-liter packs

A 50–55L pack is usually the “with breathing room” option without moving into expedition sizes.

It works really well if your kit isn’t very compact yet, or if you want extra comfort by organizing things better.

Who they’re for

• Standard kit (not necessarily ultralight)
• More food between resupplies
• Routes where you need to carry more water
• Variable weather or more extra clothing

When to choose 50L

• You don’t want to be right at the limit for space
• You’re carrying a slightly bulkier sleeping bag or clothing
• You want versatility across more types of routes

60-liter packs and above

This capacity makes sense when you really need the extra volume.

For 3-season hiking, in many cases it’s overkill.

Good for

• Winter or high mountains (more insulation, extra gear)
• Technical equipment (crampons, ice axe, rope, helmet)
• Expeditions or routes without resupply
• Very bulky gear or heavy loads

How to choose your capacity (a practical method)

Before you buy, try this:

1. Lay out all your gear on the floor.
2. Put it into a large bag or box to get a sense of the real volume.
3. Add the volume of food (about 1–1.5L per day, depending on your diet and packaging).
4. Factor in water: if the route has dry stretches, you’ll need more capacity or better management.

This method will give you a much more reliable estimate than thinking only in “days on trail.”

Quick reference

Capacity	Typical use
20–30L	Day hike / minimalist
35–45L	Ultralight trips (3-season)
45–55L	Standard kit / more breathing room
60L+	Winter / expedition / technical gear

Conclusion

If you reduce the volume of your gear, you’ll be able to use a smaller pack. And a smaller pack usually means:

• Less weight (from the pack itself)
• Better stability and less sway
• More simplicity: you carry what you need, not “just in case”

In ultralight hiking, the goal isn’t to carry more… but to carry smarter.