Metric and inches -  conversion chart for backpack volume

You see a backpack review in a magazine that touts the latest European designed spectra-clothed carbon-fiber stayed wonderpack, the perfect size for an overnight climb at 50 liters.  When you stop by the local gearhead shop, you are shown a similar looking American made model that the clerk is plugging, which holds 2500 cubic inches.  Are these two volume measurements close?  Which one is right for your needs?  When shopping for a backpack, it’s useful to know the pack size you are after in metric, typically liters, and US sizing, typically cubic inches.  Here’s a conversion table to assist you (cubic inches a rounded off).

Metric - US
20 liters - 1,200 cubic inches
30 liters - 1,800 cubic inches
40 liters - 2,400 cubic inches
50 liters - 3,000 cubic inches
60 liters - 3,700 cubic inches
70 liters - 4,300 cubic inches

Some pack volume rules of thumb:

• For a one day summit pack (Mt. Hood), look for something around 40 liters, or 2500 cubic inches.
• For packing light on a 1 or 2 night climb, consider a pack in the 50 liter range, or 3,000 cubic inches.
• And for you folks who do take along the kitchen sink, look for a honker pack of 65 to 70 liters, or over 4,000 cubic inches.