40L vs 60L vs 70L Backpack: How Much Capacity Do You Actually Need?

The Quick Guide

What Does '40 Liters' Actually Mean?

Liters measure internal volume — how much gear you can physically fit inside. 40 liters is roughly 2,440 cubic inches. It sounds like a lot until you try to fit a sleeping bag, sleeping pad, tent, 3 days of food, a cook kit, layers, and rain gear into it.

40L: A 3-season sleeping bag, ultralight pad, small tent or tarp, 3–4 days of food, cook kit, layers, and rain jacket. Doable — but only if your gear is reasonably lightweight.

60L: Everything above, plus more food (5–7 days), a larger tent, heavier sleeping bag for colder conditions, camera gear, extra layers, and some creature comforts. This is the sweet spot for most weekend-to-week-long trips.

70L+: Winter camping gear, extended resupply sections with 7+ days of food, group gear, or expedition-style carries.

The Trap: Bigger Packs Make You Pack More

Here's what nobody talks about enough: pack size changes your packing behavior.

A 40L pack forces discipline. When you can see that your sleeping bag alone takes up a quarter of your space, you start making smart trade-offs. You leave the cast iron skillet behind. You bring two shirts instead of four.

A 70L pack lets you rationalize everything. "There's room for it" becomes the deciding factor. The result is a 50 lb pack that punishes you on every climb.

Experienced backpackers consistently recommend sizing down rather than up, especially for your first pack. A slightly undersized pack that forces good decisions is better than an oversized pack that enables bad ones.

The 60L Sweet Spot

For the majority of backpackers doing 3–7 day trips in 3-season conditions, 55–65L is genuinely the right range. It's large enough to carry all your gear and 4–6 days of food without creative compression gymnastics. It's small enough that you won't unconsciously overpack.

The Osprey Atmos 65 and Gregory Baltoro 65 are both in this range and consistently rated among the best backpacking packs available. This volume range has been optimized by decades of design for the most common backpacking use case.

When Does 70L Make Sense?

Three clear scenarios:

Winter and 4-season camping. A winter sleeping bag is bulkier and heavier. An insulated sleeping pad takes more volume. A 4-season tent takes more space. You'll genuinely need 65–75L.

Extended sections without resupply. A 10-day carry requires roughly 2–2.5 lbs of food per day — that's 20–25 extra pounds of food alone.

Carrying extra for others. If you're hiking with less experienced partners or taking on shared gear (tent, cook kit, group food), you may push into 70L territory.

Frame and Fit: More Important Than Volume

Here's what most buyers underestimate: a well-fitting 60L pack carrying 40 lbs will feel dramatically better than a poorly fitting 70L carrying the same weight.

Torso length (not your height) determines what size pack you need. Most packs come in S/M/L sizes calibrated to torso length — get measured at a gear store before buying. The hip belt should sit on your iliac crest, and 70–80% of the pack weight should transfer to your hips, not your shoulders.

When in doubt, go with 60–65L. It's the sweet spot that works for 80% of backpacking scenarios. Browse our full lineup of hiking backpacks to find the right fit.