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

Posted on November 12, 2011June 8, 2016 by admin

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.

Socks:

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.

24 thoughts on “Proper Fit Explained: You Don’t Have a Shoe Size; You Have a Foot Size”

  1. Dan says:
    November 15, 2011 at 12:09 am

    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

    Reply
    1. MarkC says:
      November 18, 2011 at 4:02 am

      Dan,

      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.

      Mark

      Reply
    2. angel says:
      July 2, 2015 at 11:06 am

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

      Reply
      1. MarkC says:
        July 24, 2015 at 1:22 am

        Angel 7.5 mens is usually 8.5 women. if wide foot go for men’s size. Mark

        Reply
  2. Tom says:
    November 19, 2011 at 1:06 pm

    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.

    Reply
    1. MarkC says:
      November 22, 2011 at 11:32 am

      Tom,
      Exactly! You do recreate your arch but your feet start to look like a machinists hands.
      This is a good thing.
      Mark

      Reply
  3. Morning Runner says:
    December 1, 2011 at 10:51 pm

    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?

    Reply
  4. Audrey says:
    April 12, 2012 at 2:12 pm

    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

    Reply
    1. MarkC says:
      April 19, 2012 at 8:44 am

      yes…the stronger the foundation the better the upstream joints will function. Mark

      Reply
  5. jacob says:
    September 22, 2012 at 3:19 am

    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!

    Reply
  6. ngyoung says:
    August 20, 2013 at 2:36 pm

    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

    Reply
  7. Becca says:
    January 9, 2014 at 3:57 pm

    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)

    Reply
  8. BJ says:
    February 24, 2014 at 3:50 am

    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.

    Reply
  9. Emily says:
    August 22, 2016 at 9:20 pm

    This is fascinating to read. I’m wondering how a person with high arches factors in to all of this? I’m always told that I need *more* arch support. Will the arches just get stronger and support themselves better with a minimalist shoe? Will the arches flatten out and therefore increase my foot size?

    Reply
    1. MarkC says:
      August 27, 2016 at 10:03 am

      Emily your arches will get stronger! it takes time. muscles will get thicker too…that is a good thing. thanks for note Mark

      Reply
  10. Sally says:
    March 8, 2017 at 2:48 am

    Do you have advice for someone with a very wide forefoot and very narrow heel? At its widest point, my heel measures just under 4cm wide, and the back of my ankle is much narrower than that at the height where most shoes sit, so I can’t get shoes to stay on my feet without slipping. I already use heel lock lacing. On the other hand, my forefoot is quite wide, almost 10cm, so my toes are always squashed when I wear shoes.

    Reply
    1. MarkC says:
      March 8, 2017 at 10:48 am

      Sandals! or a shoe like Altra, Xero, Vivobarefoot or Lems. they are wide

      Reply
      1. Sally says:
        May 4, 2017 at 4:32 am

        I ordered some Vivobarefoots and they’re very narrow on the toebox and midfoot. My little toe gets pushed into the others and the side of the shoe presses on the inside of my arch. In contrast, the heels are enormously wide. I can slide my heel from left to right in the shoe while they’re laced up.

        Anyone have any good shoe-making resources? I think that’s the only way I’m going to get something foot shaped.

        Reply
        1. MarkC says:
          May 5, 2017 at 5:03 am

          sally its tough to order shoes . best suggestion is to come to Two Rivers Treads and try some on :). fit is unique like the shape of your foot. you will find the right Goldilocks fit.

          Reply
  11. Richard says:
    April 30, 2017 at 7:03 am

    Thanks for this.
    But i’m confused in the difference between basketball shoes and a running shoes. My basketball shoes are usually size 13 but when i’m trying to buy running shoes, they only have size 11 :((
    Why is that the running shoes dont have bigger sizes?

    Reply
  12. Latunlover493 says:
    February 24, 2018 at 12:20 am

    Hi I am from Mexico a recently bought a VivoBarefoot SwimRun shoes … I usually use size 8 or 40Eu …. so I tried bought the vivo barefoot size 40 but when I tried they feel enormous … even they look enormous , what should I do ?! Do I have to buy one size smaller or two ?! My feet is like 25.cm or a little less
    Thank you

    Reply
  13. Sidney Foster says:
    May 5, 2018 at 1:11 pm

    I have read your comment of shoes sizes and you forgot one biggie. Heel size! Case in point. I wear a size 14 D Sole but I have a A Heel. This cause me pain and blisters. Custom made shoes still did not address the problem. No One is sizing for the Heel and lacing causes pain and discomfort.

    Reply
    1. MarkC says:
      May 6, 2018 at 9:26 am

      thanks Sidney that is a tough one and would take some homemade modification

      Reply
  14. Martinrossow says:
    May 31, 2021 at 10:53 pm

    Thanks for sharing this Fantastic! blog.

    Reply

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