Bracket range: 41–51 L. Most packs in this range from Osprey, Gregory, Hyperlite, Granite Gear, and Zpacks will fit this kit comfortably.
Bringing a second pair of boots, an extra coat or sweaters? Pick Heavy — it adds more room in winter.
Bigger jackets and boots take more space, especially in cold seasons.
The formula
liters = 30 + trip_length_bonus + season_offset + shelter_offset + packing_style_offset + clothing_size_offset + bear_canister_offset
- Trip length: +8L per day for days 2–7, +5L per day for 8–12, +3L per day beyond.
- Season: summer −5L · three-season 0 · shoulder +10L · winter +22L.
- Shelter: tarp −5L · tent 0 · 4-season tent +6L.
- Packing style: ultralight −15L · normal 0 · heavy +10L (+8L more in winter).
- Clothing size: smaller −2L (−5L in shoulder/winter) · average 0 · larger +4L (+10L in shoulder/winter).
- Bear canister: +8L. Floor: 18L.
Sources
- REI Co-op Expert Advice: How to Choose a Backpack.
- Osprey Packs sizing guide (published pack liter ranges by trip type).
- Backpacking Light gear surveys, 2019–2024 base weight vs. pack volume regression.
Last reviewed: 2026-07-25.
Frequently asked questions
Why start with liters instead of a pack model?+
Volume is the constraint that actually limits what you can carry. Pack manufacturers publish liters, not weight capacity, because a 60L pack fits roughly the same gear whether it's a Osprey Aether or a Hyperlite Southwest.
How does season change the number?+
Winter and shoulder-season kits add insulation (bulky puffy, warmer bag, thicker pad) and often a 4-season tent. Wild10 adds 10L for shoulder season and 20L for full winter on top of the base three-season recommendation.
What if I'm ultralight?+
Choose Ultralight under “How do you pack?” and the tool trims 15L off the recommendation — a UL sleep quilt, frameless pack, and tarp shelter compress dramatically compared to traditional gear.
I bring extra boots, coats and sweaters in winter. How do I account for that?+
Choose Heavy under "How do you pack?" to add 10L, plus another 8L on winter trips. Larger clothing sizes add up to 10L more in cold seasons, because bigger jackets and boots take more room.
Can I cite this?+
Yes. Link to https://wild10.com/tools/pack-volume-sizer. The formula is published on the page.