How To Properly Size, Fit, and Adjust a Backpack

[davebugg]

Correct Sizing of a Backpack

The size of the pack is determined by the length of your spine, not by how much (volume) the pack can carry.

Measuring for a correct fit involves determining your spine's proper length. That measurement is done by using a tape measure and measuring from the protruding 'knob' on the back of your neck which is at the base of the cervical spine, to the place on your spine that is even with the top of the crest of your hips. You can do this yourself, but it is helpful to have another person assist. I recommend doing these measurements 3 separate times in order to assure accuracy, especially if doing it by yourself.

1. Tilt your head forward and feel for the bony bump where the slope of your shoulders meets your neck. This is your 7th cervical (or C7) vertebra—and the top of your torso length.
2. On each side of your body, slide your hands down the rib cage to the top of your hip bones (aka the iliac crest). With index fingers pointing forward and thumbs pointing backward, draw an imaginary line between your thumbs. This spot on your lumbar is the bottom of your torso measurement.
3. Stand up straight and measure - or have your friend measure - the distance between the C7 and the imaginary line between your thumbs. That’s your torso length.

(Video Courtesy of Kelly Collier)

Once you have that measurement in inches or centimeters, you can then look at the backpack manufacturer's sizing guide. This guide will be used to match your spine length, to their stated size range.



Sometimes a manufacturer will express sizes as Small to Extra Large. Sometimes the size scale will combine sizes like: S/M, M/L, L/XL. When the sizes are combined, it usually means that there is a good amount of adjustability to the frame of the pack to customize the fit. That will usually be in the shoulder harness and the hipbelt so that a fine-tuned fit can be achieved.


Fitting The Shoulder Harness

[Moderator note: For more discussion of the shoulder harness system, see this thread, also by @davebugg .]

First, let me mention that there are differences in the shapes of shoulder straps. The standard shoulder strap shape has been what some manufacturers describe as a "J" shape. This shape tends to fit the chest shape of the male better than the female due to the lesser fullness of the chest. However, even with some men who have bigger chests, the J strap shape can be uncomfortable.

A few manufacturers, ULA and Six Moons Design are the most notable, have developed what is called an "S" shaped strap. This shape has solved many of the fit issues for women, allowing for the straps to properly sit on the shoulders without the uncomfortable compression and chafing due to breasts of larger chests. Here is a link which shows the difference between the two strap shapes:

The shoulder harness should wrap around over your shoulders and sit slightly below the top of the shoulder. The shoulder straps should sit comfortably toward the middle of the shoulder girdle, although that may vary a bit. It should not feel like they are going to slip off your shoulders or sit tight against the base of your neck.

The sternum strap should NOT be required to keep the shoulder straps in place. The sternum strap does connect the shoulder straps, but it is designed to help control where the straps sit on the shoulders with excess pack movement; it is not meant to overcome a poor fit and placement of the shoulder straps.

After fastening the sternum strap in place, pull the adjustment strap until you feel a bit of tension.

The sternum strap on a good pack can adjust up and down on the shoulder straps. The usual placement is somewhere just below the collar bone, but body types and builds will cause a variation of where the sternum strap placement feels best.

Hip Belt Adjustments

For the hip belt, the pad of the belt should sort of 'cradle' the crest of the hip bone: the top of the pad should be slightly above the top of the crest while the bottom of the pad should be slightly below the top. Again, the belt, when it is snugged down, should cradle. The belt should not entirely sit above your hips so that the pad compresses your waist, nor should the entire pad sit below the crest of your hips totally squeezing the hip bones.

There is a lot of misinformation about how a pack's load is distributed between shoulders and hips. It is NOT true that the waist/hip belt carries the entire load of the pack. It definitely CAN do that, but doing so is undesirable.

There are reasons which might make it necessary to keep the shoulder harness unweighted and the full load weight on the hipbelt. These include damage or injury to the shoulder girdle. There are folks who prefer a total load on the hipbelt even though their shoulder girdle is healthy, but it is a practice which has potential complications associated with it. Even so, it is up to an individual to decide.

If the Hip/waist belt carries the entire weight of the pack

1. it means the shoulder harness is unweighted and there can be significant pack movement which, during difficult walking terrain, can create problems with your center of gravity. I have seen people lose their balance and fall as a result.
2. It also can result in your core muscles being overworked, stressed, and fatigued trying to compensate from that extra movement.
3. All that weight on the pelvis can create significant compression forces by requiring the hipbelt to be over-tightened to prevent it from slipping down. This can cause numbness and pain as blood flow and nerve compression is experienced.
4. All the weight on the hipbelt will also place additional strain to the hip sockets and knees.

The load ratio will be about 5 to 15 percent for the shoulders and 85 to 95 percent on the hips. This will allow for the proper engagement of your core muscles to help carry the backpack.

Steps To Adjusting a Backpack Before Walking

I'll add a link to a video (ignore the manufacturer) that shows steps to follow when putting on a pack and adjusting it. The basic steps are these:

1. Loosen all the straps on the shoulder harness and hip belt.
2. Put on the pack and very slightly tighten the shoulder straps so that the hip belt is slightly below the hips.
3. Fasten the sternum strap, keeping it slightly loose.
4. Shrug your shoulders up, and then fasten the waist belt and getting it roughly into position.
5. Slightly tighten the shoulder straps to assist with the hip belt adjustment.
6. Position the hip belt padding to let the padding sit half above and half below the crest of the hips. The padding of the belt should never sit entirely above the hips. The padding should sort of wrap itself over the top of the hip bone and hug the hips.
7. Tighten the belt just enough to keep it in position. At this point, nearly 100% of the packs weight is resting on the hips.
8. Snug the shoulder straps to take up 5 to 15 percent of the packs weight. You will feel just a slight unloading of the weight off the hips.
9. At the top of the shoulder straps and toward the pack, are smaller straps called 'load lifters'. Grasp them and pull to your front. You will feel the weight of the pack lift up slightly and pull more snugly toward your back. This helps with center of gravity and balance. You can experiment with how snug or how loose you want to pull on the straps. A properly adjusted load lifter strap will form a sort of 45-degree angle when viewed from the side.
10. On some waist/hip belts there can be a small strap connected to each side of the belt. Again, pulling forward on those straps will bring the bottom of the pack closer to your back, helping with balance as you are walking.

It is important to remember that after you make the first pack adjustment before starting to walk, that you will frequently be changing those adjustments while walking: tightening, loosening, pulling, having the pack higher or lower....

Pack adjustments are a dynamic thing, not a static thing. As you walk, how the pack feels, pressure points, center of gravity, etc. WILL change. Therefore it is important to become so familiar with your pack that making adjustments becomes second nature as you walk, requiring no real thought or consideration.

A good pack, loaded and adjusted properly, will be so integrated to your body while walking that you sometimes forget you are wearing it. Now, NOTHING will make a weighted load in a pack disappear, but it will help keep that load from becoming an agonizing exercise in torture.

 

[davebugg]

I would like to add an additional consideration for those who find that they have a hard time getting all the parts of a backpack to fit and feel good. Those are folks who are normal but disproportionate with various areas of the body. A waist size that is larger and hips that are narrower, for example, or a larger chest but with a narrower shoulder width. We all come in different sized and shaped packages.

If you cannot find a good fit, the answer might be to seek out those manufacturers (and models of backpacks) which allow the swapping out of hip belts and shoulder straps. There are a number of backpack makers who offer these features in some or even all their backpacks.

Although not as customizable are those backpack choices which allow for a good amount of adjustment to the size of the unfastened hipbelt and minor adjustability to the length of the backpack frame.

 

[Adelina]

Very explicit - thanks so much!

My experience on the Camino (and while backpacking) is that you are right - if fitted correctly, the pack becomes one with the body!

 

[Mr_Ross_Duncan]

Thanks Dave, great information and very helpful.

 

[OTH86]

Thanks, Dave! I seem to have lost some spinal length, and wonder how this affects the load lifters. I can't seem to tighten them enough - thoughts? Is it possible to take a tuck using (industrial) sewing machine?

 

[davebugg]

Thanks, Dave! I seem to have lost some spinal length, and wonder how this affects the load lifters. I can't seem to tighten them enough - thoughts? Is it possible to take a tuck using (industrial) sewing machine?

If you have lost spinal length, then the shoulder harness tends to sit too high because of the hip belt's position when fastened. This causes the load lifters become less usable.

 

[SirRon]

Thank you so much for this info!

 

[Judeperegrino]

Thank you so much, incredibly informative. I have some questions I so hope you or others might answer ... about women's bodies and women specific packs. I have a thin small torso but large hips (and butt) that not only were great to carry children on but I find the best place to carry my backpack: as in I position my waist strap above the hips, so the pack sits on them a bit like my children when they were little... In effect would this means getting a pack for a very small torso? Smaller even than if I was positioning the waist strap around my hips as I notice most men do. How might I measure this situation? My trip to a few local very reputable mountain equipment shops left me confused: there is so much to consider and no one offered to take that kind of care that you train staff to do. Ages ago I lucked out with a women's Deuter pack which is not ultralight but happens to fit brilliantly but this is for multiway pack walking in remote rugged areas carrying all food, tents etc etc not the camino. Hope this makes sense and hope OK to ask for this advice! with thanks again

 

[davebugg]

Thank you so much, incredibly informative. I have some questions I so hope you or others might answer ... about women's bodies and women specific packs. I have a thin small torso but large hips (and butt) that not only were great to carry children on but I find the best place to carry my backpack: as in I position my waist strap above the hips, so the pack sits on them a bit like my children when they were little... In effect would this means getting a pack for a very small torso? Smaller even than if I was positioning the waist strap around my hips as I notice most men do. How might I measure this situation? My trip to a few local very reputable mountain equipment shops left me confused: there is so much to consider and no one offered to take that kind of care that you train staff to do. Ages ago I lucked out with a women's Deuter pack which is not ultralight but happens to fit brilliantly but this is for multiway pack walking in remote rugged areas carrying all food, tents etc etc not the camino. Hope this makes sense and hope OK to ask for this advice! with thanks again

First: If you have the Deuter, pack, I would not rule it out for use on Camino. In fact, it might be the ideal solution. I have several backpacks that hold a variety of capacities since I do winter backpacking, a lot of training day hikes, and 3 season backpacking that can last for several months.

It is that three season capacity backpack, a 60 liter, that I always take for a Camino. It fits well, I do not have to tightly pack my stuff, and it feels great. I don't care if I could save a pound by using my 30 liter daypack, I like how my 60 liter backpack feels and carries when I wear it. Funny thing, on most day hikes I also use the 60 Liter backpack, too.

Onto the question at hand.

Think of the hipbelt as having three sections: Top, Middle, and Bottom. The supportive part of the hipbelt is not the bottom section, it is the middle section.

The effect of supporting a child or a laundry basket with the 'crest' (top, rounded part of the hipbone) also allows the child (or basket) to slightly snug into the area just a tad bit into the space just behind and below that hipbone crest. The TOP crest of the hipbone provides the supportive 'ledge', but the child's weight seems to also snug into that small space as well.

It is the MIDDLE section of the hipbelt that supports the load. The bottom section and upper section of the belt should wrap around the curve of that upper Crest of the hip bone. Without seeing you with a backpack on, I suspect that measuring the length of your spine, from where you feel the Crest of your hipbone as it protrudes, to the knob at the back of your neck as you look downward, will be a very close fit. This should come close to being the correct size for your pack.

Now comes the art of assessing the backpack for proper sizing and fitting.

Load the pack with 20 pounds/10 kilos. I like to use an amount of weight that is noticeably heavier than the planned, average load I will carry. I want to make sure that the hipbelt is under the stress of a load for when I do a final evaluation of the backpack's fit.

Next, follow the steps listed in my first post above as you put on the candidate backpack. This will help to assure that a proper visual confirmation of the backpack's fit and size is correct.

If I am checking a person, I want to make sure the upper edge of the hipbelt is slightly curved over the crest of the hips, I am looking at the fully adjusted harness to see that the shoulder straps are wrapping over the shoulder correctly, and looking at the angle of the load-lifter straps to make sure that they are indicating a correct fit.

Then I am checking that the chest strap is able to be positioned comfortably on the chest and adequately adjusted. I am examining the shoulder straps to determine that, for women and chesty men, the straps do not cut into tissue or otherwise pinch or unduly compress those tissues.

If that last part is overlooked and because the shoulder straps should carry about 10% of a backpacks weight, bruising and skin damage can occur if the cut (shape) of the shoulder straps are not correct for your shape and size.

I am aware that some believe that all the weight should be offloaded from the shoulder straps onto the hipbelt. For normal health and condition of the shoulder girdle, that is not correct information, In order to assure the ability to keep your balance while walking, to fully engage your core muscles to help with distributing the carried weight, and to keep the backpack from swaying while worn, the shoulder straps MUST be under a bit of weight/tension. If adjusted correctly, the felt tension is virtually nil and induces no noticeable effects to the shoulder girdle when wearing the backpack for 8 to 12 hours of walking.

However, shoulder injuries or anomalies may necessitate completely unweighting the shoulder harness and suspending all load to the hipbelt, There are methods that can help compensate in adjustments that will minimize off-center gravity issues creating balance problems.

 

[Judeperegrino]

you are a godsend thank you! If only we could all have someone like you to help us on site! I still remember a LONG time ago my first multiway bushwalk with my father's pride and joy the Mighty Mule by Paddy Palin he bought circa 1960 with a huge square frame ... great on a burly square-chested bloke but on my slight ballerina frame it just banged into my butt as I walked and I felt like a humble beast of burden!
The first waist straps were an amazing improvement but then things got even better and the story continues...narrow packs, women's packs, adjustable packs, sized packs. Only thing is then one feels overwhelmed as to which one is best for the job!
I have Ehlers Danlos Syndrome (EDS) which is no big deal but it simply means I am hyper mobile and skin is very fragile and easily bruised and cut and then I bleed a lot ..and need to be more or less wrapped up in cotton wool.I bruise if you take my blood pressure! So having the shoulder straps cut into one is a big problem. Or the sternum straps being too tight and I go for the most padded variety ... (same when buying hiking shoes: the tongue and area around the ankle need to be super padded).
The last complication is that my dermatologist prefers me to go for the packs that have a ventilation back spacer as I get a rash from sweat glands not functioning super efficiently and the rash doesn't simply go away...
You are an amazing source of detailed info and I am most grateful and hope again this might also be helpful for other women with slight and short torsos but wide hips. Sure says no size fits all ...

 

[Judeperegrino]

Hi Rick again ... the EDS means also super bendy (can do an awesome backbend even at my not so young age) ... complicates things because the more the pack just kind of snuggles into my back and becomes part of me the better as long as I am able to walk well with good posture.
Having said all this for a 40 litre style size any recommendations welcome. The multiway large Deuter a bit too large for this job I fear...