To learn how to fit a backpack properly there's one all-important number you'll need to know first: your torso length.
What lots of people don't realise is that backpacks come in torso sizes ranging from extra small to extra large.
But a tall person won't necessarily need a large size and a short person won't necessarily fit a small one. And two people of the exact same height could have two completely different torso lengths!
Not quite as critical but also essential is your hip size.
The hip belt at the base of your backpack can take almost all the weight of the pack off your shoulders, but it's got to fit right. And the heavier your pack the more important this is.
So, before you do anything else, get ready to take those measurements.
Knowing how to fit a backpack correctly starts with knowing the length of your torso. You can't actually measure your own torso, though (at least not very accurately), so you'll have to invite a friend over first.
Then, with your friend behind you:
If you can't find this vertebra with your head bent forward, try bending your head backwards. You should be able to find the bone right in the crease of your neck.
If you haven't got a flexible measuring tape just grab a piece of string or some masking tape. Then, follow the same six steps using the string or tape instead of a tape measure. When you're done, measure against a ruler.
Take down this measurement and move on to the next.
When you're looking at how to fit a backpack for maximum comfort, your hip measurement comes second only to your torso measurement.
The idea of a hip belt on a backpack is to transfer the weight of the pack from your shoulders to your hips, closer to your centre of gravity where the load is easier to carry.
Not surprisingly, a hip belt sits on your hips. So for it to fit properly you need to measure your hip size.
Then why is a hip belt so often called a waist belt? Good question!
To measure your hip size:
Check in a mirror to make sure you've measured at an even level all the way around.
As with your torso length measurement, if you don't have a tailor's flexible measuring tape a piece of string or some masking tape and a ruler will do.
And that's it! You know how to fit a backpack.
Jot down this measurement and get ready for sizing.