Pack size for a thru-hike depends far more on the longest stretch of food a hiker carries between resupply points than on the trail's total mileage. A trail with towns every three to four days needs less capacity than one with six- to nine-day carries, even if the second trail is shorter overall.
A useful starting guideline: budget roughly 30 to 40 liters for a three-season sleep system, shelter, clothing, and cook kit, then add roughly 1.5 to 2.5 liters of additional capacity for each day of food carried beyond a base three- to four-day resupply cycle.
That guideline plays out differently across the major U.S. long trails:
- Appalachian Trail hikers commonly use 45 to 65 liters, since most resupply carries run three to five days, with Maine's 100-Mile Wilderness as the main exception.
- Pacific Crest Trail hikers commonly use 40 to 55 liters, reflecting the trail's graded tread and lighter average kit, though a Sierra Nevada bear canister adds several liters through that stretch.
- Continental Divide Trail hikers commonly use 55 to 65 liters or more, driven by the trail's longest average carries and heavier navigation gear.
- John Muir Trail hikers commonly use 50 to 65 liters, driven by a mandatory bear canister and sparse resupply points across roughly 210 miles.