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Backpack Cubic Inches: A Thru-Hiker's Guide

Updated on October 17, 2009

Shopping for a backpack can be an overwhelming experience for the novice thru-hiker.  The weight of the world seems to be riding on your choice.  After all, this pack will be your “home” for six months!  I often get questions from future thru-hikers about cubic inches.  What does this number mean?  How important is it?

Backpack manufacturers use cubic inches to define the storage capacity of a backpack.  It includes the main pack space as well as any outside pockets.  Don’t let this number scare you.  I have hiked 8,000 trail miles but I still had to Google my backpacks to find out their cubic inch capacity.  The number is not what’s important.

To truly get a feel for whether or not a pack is roomy enough for your gear and carries well, you will need to test it out.  I would recommend finding websites that offer free shipping of merchandise.  When the pack arrives, load it up, try it on, adjust the straps all you want and if you don’t like it send it back.  The only cost you’ll incur is the return shipping fee – a small price to pay to make sure you get exactly what you want.

When you are testing a pack for volume, here are some things to consider:

Where to Start

Start small with a cubic inch capacity of 3000 to 3500.  Try not to go over 4000.  On my PCT thru-hike I carried a Granite Gear Vapor Ki (  This pack has a cubic inch capacity of about 3500 and it was roomy enough for me to carry a week’s worth of food and full winter gear (including an ice ax) into the Sierra Nevada Mountains.

Pack Weight

Your pack weight starts with the weight of your empty backpack.  If you choose a backpack that weighs five pounds, you are already carrying five pounds before adding any gear.  Look for a pack that weighs between two and three pounds.

Your total pack weight should never, ever exceed 25% of your body weight.  If you are an ultralight backpacker, your pack weight should not exceed 20% of your body weight.  Therefore, if you are a 100 pound woman, you should shoot for a 20 to 25 pound pack.  Remember that the lighter your pack, the more enjoyable your hiking experience.  If you get your pack weight down low enough, try a few ultralight backpacks and see how they feel.  I would recommend the GoLite Pinnacle (

Here is a simple formula for calculating your pack weight:

Empty pack weight + gear (base) weight + 2 pounds of water (1 liter) + 2 pounds of food per day

How to Pack

The best way to determine if a pack is going to be big enough is to load it up with your gear and see how it feels.  When packing a backpack, remember to keep the heaviest gear items (such as food) close to your back.  Center the weight over your hips for better balance.  Lighter items can go on the bottom and items of medium weight can fill in the rest of the space.

How it Carries

If your pack is uncomfortable, try repacking it and readjusting the weight distribution.  This could make a big difference.  You can also make changes to the hip belt and load lifter straps on your shoulders to adjust how the pack carries.  If the pack is uncomfortable no matter how you adjust it, you might need a pack with a better suspension system to handle the weight of your gear.  Or you could reduce your gear weight and try again.


You definitely do not want to take your pack off every time you need access to water, a snack or other frequently used items.  Forget the numeric value of cubic inches – just make sure the pack you choose has adequately sized side pockets.  Fill them up with anything you want easy access to including water bottles, snacks, sunscreen, insect repellent, maps and guidebooks.  If you can’t reach back easily and snag these items, you probably want to find a different pack.

Try out a couple different packs taking this information into consideration.  And remember – cubic inches are to backpacking what age is to love.  Just a number.


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    • Hokey profile image

      Hokey 7 years ago from In the energy.

      I am hiking the Appalachian trail this fall. I can use this! Great Hub! Thanks. Namaste

    • wings4me1 profile image

      wings4me1 8 years ago

      fantastic article, great information