Custom Cubic Inch to Liter Calculator (or Liter to Cubic Inch) 1  Daypacks will be under 2,500 cubic inches or 40 liters. 2  Weekend packs are typically 2,500 to 4,000 cubic inches or 40 to 65 liters. 3  Weeklong packs range from 4,000 to 6,000 cubic inches or 65 to 95 liters. 4  Expedition packs are 6,000 cubic inches or 95 liters and up.