Proper Fit Explained: You Don’t Have a Shoe Size; You Have a Foot Size

In the past three years, I have completely rethought how a shoe should fit. More accurately I now think about how a shoe should fit rather than just pick a size.  Since I started running more true barefoot miles over the last year my foot size has greatly increased in thickness. I can no longer wear any shoe that I owned six months ago.  My Newton running shoe size has increased from 11.5 to 12.5 and my next pair of VivoBarefoot Evos will be a 46.  I had started comfortably in a 44, now wear 45 without an insole and wish there were more room

At Two Rivers Treads, which just launched an online store to complement our brick-and-mortar store in Shepherdstown, West Virginia, we defy old-school thinking of sizing and narrow-shaped, ill-fitting conventional shoes. Improper shoe sizing and shape are the primary cause of ingrown toenails, bunions, corns, hammer toes, and hallux valgus.  Shoes that don’t fit your feet correctly can also lead to muscular imbalances in the body, leading to foot, knee, and hip injuries.

A proper fit accounts for the natural expansion of the foot upon ground contact. Excess waste is eliminated, along with everything that inhibits your foot’s natural motion. So your foot is free to move and work the way nature intended it to; the way of its own barefoot motion.  Call it toe wiggle freedom.

Yet, with sizing, most get it wrong

The naturally thickened feet of Dr. Daniel Lieberman, Ken Bob Saxton, and Dr. Mark Cucuzzella. Photo taken by Nick Pang at the NYC Barefoot Run sponsored by Merrell.

First, abandon the notion that you have a shoe size. Instead you have a foot size.  Shoes are made all over the world and apply different shapes and standards. If you measure your foot seated with a traditional measuring device like a Brannock Device and base your size on that you will likely be off by 1-2 sizes when applied to a running or hiking shoe.  One shoe size is only 1/3 an inch.

Also critically important is that the Bannock device measures the widest part of the shoe at the ball. Infant feet are widest at the ends of the toes, not the ball of the foot. The natural alignment of the human foot is where the metatarsals directly align with phalanges (toes) and get wider than the ball of the foot.

Here’s why most sizes are too small:

When a load is applied to a foot by running or with a pack weight your foot will spread in length by up to half an inch

You need at least an 1/8 inch or more space on heel and toe for any sock.

You want 1/3 to 1/2 an inch in front of your big toe to allow room for loading and splay

Your foot will splay 15 percent in width under load.

Your foot is widest at the toes and unfortunately most shoes are not shaped this way.

Tips on sizing. 

At Two Rivers Treads, we never had a customer return shoes because they too were too big.

Do not assume you are the same size as a previous shoe.

Take your time and try several shoes on, preferably at the end of the day. Go run in them. Do not try them on sitting.

Always try both shoes on. If feet are slightly different size fit the larger foot.

Take the shoe removable insole out and see how your foot fits against the insole as a template. Is there room at the toes or does you foot spill over the insole?  If no room to spare or if your foot spills over this shoe will not fit comfortably.

Keep going half size up until the shoes are obviously too big.

Try on shoes at end of day when feet are most flattened and swollen

Try on with the type of sock you will wear for activity.

For women, you may fit better in a men’s shoe for width.

Do not lace the shoes up tight.  Allow spread in the midfoot and forefoot.

Go up onto the ball of the foot. Can you put your index finger between your heel and the back of the shoe- if not likely too small.

Consider not using the soft insole.  This takes up space in the shoe and interferes with ground feel.

Walk on a firm surface, not a carpeted one.

If you are a runner you must run in the shoe.  What feels nice and soft when walking is the opposite of what you need when running, which is a more firm base to give the message up your kinetic chain to stabilize.

Sandals are great as they allow for natural foot spread without restriction from an upper.


When trying on shoes, wear the socks you would normally wear in them. Socks are not necessary but are mainly for added comfort, especially in avoiding blisters. Like shoes, socks can be too tight, contributing to foot irritation and restriction. For most situations, socks should be thin and not tight.

Make sure your socks do not bunch though.

Thicker winter socks may require a half-size larger shoe.

Which style of socks you wear (low-cut or above the ankle) and what they’re made of (natural fibers such as wool or cotton, or a blend of synthetics) is up to you. But like shoes, make sure they fit well; and be careful to avoid the sock interfering with shoe fit. My preference is merino wool of light synthetic blend.

13 Responses to “Proper Fit Explained: You Don’t Have a Shoe Size; You Have a Foot Size”

  1. Dan says:

    Interesting take on sizing. I always use size 10 as a starting point and buy the size that feels the best. I have a fairly narrow foot and have good luck with Salomon in size 44 for rugged hiking and trail running. Most warm weather hikes and runs are done in a Merrell Trail Glove in size 43.5 and which I find to be the most comfortable shoe I have. My Vibram TKO is a 42. If I size my shoe as you suggest I would have a lot of slippage resulting in blisters. I now wear minimalist shoes most of the time, mostly Merrell which have lots of forefoot space but fits like a sock in the heel. Never wear shoes in house. I just don’t see much reason to go all the way to barefoot for outdoor activities; perhaps that will change when warmer weather returns next spring

    • MarkC says:


      You are already sizing correctly from your description with happy feet and in shoes with wide toe boxes. most do not have the insight that you have as you are varing size based on the fit. Salomen narrow toe box (44) Vibram no toe box (42). Plus you are trying them on and running in them….right on.


    • angel says:

      Can you tell me what size is a 7.5 womens running shoe.Is it a size 7 1/2

  2. Tom says:

    I expected that running in minimalists shoes would gradually reduce my foot size because my foot is fairly flat and I figured the arch would slowly rise. While my arch does seem to be increasing a bit, I’ve noticed my shoes getting smaller and smaller. I guess that makes sense though. Since I’ve started taking trapeze classes my hand has increased in size. I guess if you’re using something it builds muscle and muscles makes hands and feet larger.

  3. Morning Runner says:

    Another interesting article. I remember reading in the Born to Run book of people dropping shoe sizes as their arch returned and I thought I might experience the same as my flat feet disappear. However my experience is I am now a size bigger which I guess is a good thing. Even if as we say in Scotland that gives me big “muckle” feet. I wonder if the five fingers might allow for a drop in size as there design is wide anyway?

  4. Audrey says:

    My feet are definitely getting bigger in all directions as a result of wearing minimalist shoes. Knees seem better too which is a great bonus

  5. jacob says:

    I am picking up a pair of the new balance minimus trail zeros. They have a huge toe box. That makes selecting a size a little difficult. I usually wear 10 or 10½. But in these I tried on 9 to 10½. I believe 9½ felt best. But I am going to try them on again before I buy. When I have plenty of time. I believe the dicks in my area will let you run on a treadmill in their shoes. Unfortunately nobody in my area carries the trail zero. So I am trying on mt20’s to figure out my size, then ordering the shoes. I hope that method works. I am so eager to buy these shoes!

  6. ngyoung says:

    Problem I am having with my Merrell Trail Glove2’s are that I think my right foot is leaner then my left. My right seems to shift around in the shoe too much. I tried on 11 and 11.5 and went with the bigger size thinking they would swell more when I walked or ran and didn’t want them too tight. Unfortunately for about 70% of the time I am wearing them I can’t keep my right foot seated in the shoe properly even when lacing it tighter then my left and just starts to hurt the top of my foot from the laces digging in. Too loose and it feels like the bottom of the shoe is shifting to the outside of my foot.

    Once I actually get running though it all seems to start to go away which is when I think it swells just enough to not move around as much anymore.

    Next time I think I will size for my smaller foot if I get another minimalist shoe. I think where I went wrong is that I was too concerned about it being too snug where it was supposed to be snug. The toe box and heel were fine just in between on the mid foot was tighter then I was used to and I didn’t

  7. Becca says:

    I am trying to get my first merrell running shoes and I was wondering about the proper shoes size. I normally wear a 7.5 but usually its very snug. should I get a 8 in the merrell shoes or do they automatically have more room in the toes so i would stay with a 7.5 (toes usually touch or almost touch the end of shoe)

  8. BJ says:

    My worry isn’t between sizes, but finding a good shoe that fits period! There store device says 14, but to get a fit i get 15 shoes. Merrell BA2 in 14 is a perfect fit (maybe get then) Skechers GB Trail in 14 are great,too. Stores don’t have shoes for me to try on, that is a problem.

Leave a Reply

Your email address will not be published. Required fields are marked *