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Shoe size calculator

Discussion in 'Classic Menswear' started by niklasnordin, Mar 5, 2013.

  1. DWFII

    DWFII Bespoke Boot and Shoemaker Dubiously Honored

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    The thing to remember is that the foot can feel 1/16" in circumference. Full length sizes are calibrated in 1/3 of an inch (more or less) from what is almost always an arbitrary baseline depending on the last. Width grades roughly 3/16" per size at the treadline and half of that at the heel seat. it's actually more complicated than that because last grade up in length for each increase in width. But these can be critical factors in proper fit esp. with regard to length and width in the forepart of the shoe.

    Then too, some people have dense feet, some have flaccid feet. Some people have strong connective tissue, some not so much. Some people hold more or less fluid in their feet. Do you know how to pull the tape measure to get a girth measurement that you can send off to someone with full confidence that the resulting size will address the type of foot you have? Do you know what kind of foot you have?

    Does this system address heel seat width? Does it address treadline/joint width?

    Does it address the fact that the length measurement...esp. as take the way this system suggests...will hardly ever accurately predict the correct shoe size, simply because some people have long toes, some have short toes--the only accurate way to find the proper shoe size is to measure the heel-to-ball length.

    I don't doubt that this is clever and nor do I doubt that in many cases it will be close enough...but there's an old saying in the Trade that has application--"The shoemaker that says that he has never had a misfit is either lying or needs a new standard of fit." Most people buying RTW shoes have never had a really really good or accurate fit. The upshot is that unless your system addresses the issues I've outlined above, it is really not much better that a person just trying a pair of shoes on and going with what feels OK.

    Bottom line is that without a standard of fit that is universally recognized from one maker to the next, one last model to the next, among all customers, self fitting is probably the closest thing to infallible...esp. when you consider that probably half of fit has no bearing on the foot at all but is rather in the customer's head.
     
  2. niklasnordin

    niklasnordin Senior member

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    I agree with you 100%, but when you see a beautiful shoe online that you have no way of trying before buying it...what to do?
     
  3. Claus

    Claus Senior member

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    If I understand you correctly, param_1, param_12, etc. would be foot measurements. Unfortunately, they are highly correlated. A Least Square estimation could result in a rather artificial foot shape that nobody has.

    However, I could try over the weekend. Is there any particular last you're interested in? Maybe, one you could test in the following week?
     
  4. Claus

    Claus Senior member

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    DWFII,

    I understand your ideal fit as a custom shoe maker is something that the system will never attain. But I doubt it can be reached with RTW, anyway, unless one is really lucky.

    The market today favors RTW and most people are only interested in getting the shoe they want in a somewhat comfortable size. When the latest SF frenzy starts, people simply buy a Carmina, or Meermin, or Vass, or whatever. Could this be possible if they really cared about 1/16" differences in circumferences?

    I appreciate the input, though. :)
     
  5. niklasnordin

    niklasnordin Senior member

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    yes, thats what param_1 means. Its true that they are correlated, so it could present problems, in which case I guess it would be safe (well pretty safe) to exclude that parameter.

    I have a EG in last 888, could be a good trial last.
     
  6. DWFII

    DWFII Bespoke Boot and Shoemaker Dubiously Honored

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    Well, the point I was making in my above comments is not that everyone will appreciate a bespoke fit. You're correct, RTW is the name of the game. But think of what that means--it's all down to subjective perceptions. Even in bespoke work, if a fitter's model is done, the customer still tries it on and either accepts or rejects the fit based on what is still probably, entirely, subjective perception.

    So...if it's all subjective, there doesn't seem to be any point in trying to codify fit from a limited, and limiting, set of even more subjective (the untrained customer taking his own) measurements.

    And I suspect that's the reason, after all these decades and centuries, the amount of standardization in lasts and last grading is almost immaterial.

    PS...not trying to diss you or make light of your ideas...simply pointing out the remorseless facts. BTW, if you want to get semi-accurate measurements from a foot...there's already a computer based scanner out there that will do everything but compensate for types of feet and/or subjective perceptions.

    --
     
    Last edited: Mar 6, 2013
  7. Claus

    Claus Senior member

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    Ah, there's the other problem. Least Square requires enought data to estimate the vectors a and b. I don't have enought ratings for EG's 888 last.

    I'll use the 348 by C&J in E and report back after the weekend.
     
  8. niklasnordin

    niklasnordin Senior member

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    ah, crap :)
    348 will do fine,

    cant wait to see what will pop out.
    cheers
     
  9. Claus

    Claus Senior member

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    Niklas, I'm back, as promised. Beware, this is going to be a bit geeky…

    If I understood your suggestion correctly, the goal is to find a, well, "reasonable" shoe size for a given last-width combination (hereafter called 'last') based on one's foot measurements.

    Given the goal, Multidimensional Least Squares seems somewhat plausible: Instead of using only foot length as it's traditionally being done, it also considers the potential influence of ball width, heel width, etc.

    Since Sizeadvisors uses 6 measures for each foot and there's also a fixed term, we need to estimate at least 7 parameters. Which means, we need at least 8 data points for any last. Which means somewhere between 4 and 8 ratings of 3 or 4 stars, depending on whether the measurements differ for the left and right foot.

    Using left and right measurements (in Millimeter) separately, Least Squares yields

    Code:
    Foot length:   0.100271900057
    Ball girth:    0.0125457488365
    Ball width:   -0.0379630679714
    Heel width:   -0.0241301798012
    Instep girth: -0.00839712226414
    Heel girth:    0.017940791048
    Constant:    -20.2175416295
    Consequently, your measurements result in an suggested shoes size for C&J's 348-E last:

    Code:
    Left:  5.75438715856
    Right: 5.75438715856
    According to this, you should try a 6.0 UK for this last. For comparison, using Sizeadvisors formula based on foot length alone, would result in the following suggestion:
    Code:
    Left:  6.03
    Right: 6.03
    Since shoe sizes are rounded up, this would yield a 6.5 UK which I guess is more appropriate given your other ratings. A 6.5 UK is also the recommendation for you under 'Similar fittings'.

    So, considering only this example, Least Squares doesn't seem very promising. However, it should be noted that you didn't measure very carefully. While every algorithm has the "junk in, junk out" problem, some are more forgiving. Least squares can capture the mistakes made by others to some degree, but it can't capture your own mistakes.

    It's also a black-box method. There's no way to interpret the results in any meaningful way, other than stating that some dimension are relatively more influential, while others may even have a negative influence. Each parameter thus probably catches some of the "real" weights if there is such a thing but each also catches

    • the influence of converting the measurement scales (from mm to shoe size).
    • the average preferences of all raters of the particular last.
    • some measurement errors if their distribution differs from the assumed distribution.
    • other factors that may exists.

    That doesn't mean Least Squares can't be helpful, but it's probably more useful for large samples to extract factors that influences a recommendation.
     
  10. niklasnordin

    niklasnordin Senior member

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  11. Claus

    Claus Senior member

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    Glad I could help. Drop me an e-mail if you need anything else. I always enjoy talking to someone who is interested in shoes and also able to talk geek. ;)


    Hopefully, you don't mean to play with your measurements. This is like scientist "playing" with the data to get the result he wants.

    To give you an impression, how measurement errors reflect any estimate:

    I also tried using Least Squares in a "disjunctive" approach (repeated two-dimensional) which seem more in line with what my sources tell me about grading. They say, for every last length increment in mm, there's an corresponding increment in all the other dimensions in mm.

    So, I constructed a "reference last" that would be perfect for an average foot shape of Sizeadvisors' members. Since an increment of half a unit in UK sizes is an increment of 4.235 mm in last length, my current estimates for the grading procedure are thus:

    Code:
    Foot length:    4.235 mm * 1          = 4.235       mm
    Ball girth:     4.235 mm * 0.54524508 = 2.309112914 mm
    Ball width:     4.235 mm * 0.25838468 = 1.094259120 mm
    Heel width:     4.235 mm * 0.18921089 = 0.801308119 mm
    Instep girth:   4.235 mm * 0.58475284 = 2.476428277 mm
    Heel Girth:     4.235 mm * 0.99456132 = 4.211967190 mm
    
    Put differently, mis-measure your ball width by a mere Millimeter, and your shoe size estimate for the "reference last" might be off half a unit if we would only consider this unit.

    To be honest, your current measurements don't reflect a high instep.

    Your instep is probably best indicated by the (short) heel girth measure. When I compare your values to the expected average for someone with your foot length, yours lie 8.359mm below the expected value. This translates to almost a full size on Sizeadviors' internal "reference last".

    In other words, if we'd only consider heel girth, you should be wearing a UK 5 on Sizeadvisors reference last.

    Although this is not the same as C&J's 348 last in E, I still found the information useful. First, I expect every last to behave like this. Second, the average last probably reflects the average of all available lasts to some degree.
     
    Last edited: Mar 11, 2013
  12. niklasnordin

    niklasnordin Senior member

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    This is really interesting.
    Here's a pic of me wearing a 348 Edgware size uk6.5,
    http://instagram.com/p/MgTZIXNn2s/

    if you look at the gap at the shoe-laces this, to me, suggests that the shoe is slightly too small.
    But, if you look at the creasing at the toe, this, to me again, is an indication of that my shoe is slightly too large, especially the right shoe,
    which has a very unfortunate way of creasing, that I think stems from not breaking them in properly.
    If I remember correctly these were the 2nd pair of C&J I bought and the first on the 348 last and I just put them on and started to use them.
    Since then I've read that you should not do this :)


    > Hopefully, you don't mean to play with your measurements. This is like scientist "playing" with the data to get the result he wants.
    That is what I meant, but not to 'get what I want'.
    As you say, its quite sensitive to how you measure and my assumption was just that given any data set, the error is bound to be at least a few
    millimeters. So my idea was to use the 'fit-function', to get a recommendation for different sizes.
    Some people are perhaps smack dead center in the 6.5 size, which would require the data you enter to be less accurate.
    Others might be 6.5, but very close to a 7,so the smallest error in their measurements would give 'wrong size'.
    However, this might not necessary be a bad thing since they could use both (all depending on personal preference)

    If I give you a scenario...
    I enter my data and out comes something like this.
    Your size is: X. depending on the accuraty of the data you have supplied there are indications that you could also be a size Y.

    Now my collegue wants me to get back to work, so I have to pick this up laters :)

    thanks for the updates. I'd be interested to see how this develops
     
  13. Claus

    Claus Senior member

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    I believe, I've seen worse for the 348 last.

    To me, the creasing at the toe suggests that the toe spread (Hm, hopefully, this is the correct translation) is too low relative to the toe allowance. This can happen if one buys shoes too large (ie. too long). But it can also happen if the last is elogated, and the last designer didn't raise the toe spread accordingly.

    As far as I know, deeper creasing seems rather common for the 348. After all, it's an elogated last. A shoes tip is presssed upwards, anyway, when one walks. But the forces are a bit stronger for elogated lasts unless the toe spread is higher, too.

    Additionally, if your right foot is a tad shorter than your left, different creasing patterns seem to be rather common.

    The gap at the shoe-laces indeed suggests that your instep is high relative to the last and size. But without knowing how the last behaves in relation to the average, it's hard to make a judgement.

    Also, let's not forget that Sizeadvisors sample might be biased. Or maybe, I made a mistakes somewhere in the calculations.
     
  14. Lustro

    Lustro Member

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    So Claus,

    My heel girth is 365 mm (for US length 11.5). Would that indicate a low, medium, or high instep?

    Thanks
     
  15. Claus

    Claus Senior member

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    I'd need your foot length(s), measured while standing upright (preferably in Millimeters).

    The info "US 11.5" is too ambiguous: It can mean "this is what I wear usually" which is often false when one has a low or high instep; it can mean: "this is what I was measured" and then there's the problem of the various differences between measurement devises.
     
  16. Lustro

    Lustro Member

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    Oops, double post....
     
    Last edited: Mar 18, 2013
  17. dg626

    dg626 Member

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    toes: 24 cm
    instep 26 cm
    length: 26 cm


    Wow, just did this. I have almost identical measurements to OP.
    Toes: 23.5cm
    Instep: 26cm
    Length: 26.2cm

    Any idea what size you are in Vass and Carmina Simpson Last?
     
  18. niklasnordin

    niklasnordin Senior member

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    sadly no, I've been drooling over the Vass thread for a while, bit I dont dare to order a pair.
    I havent tried the Simpson last, but on the Rain I'm using 7.
     
  19. niklasnordin

    niklasnordin Senior member

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    so true.
    There is a guy on your site with very similar measurements to mine that thinks size 8 on the 348 last for C & J is a good fit, albeit with a pair of thick socks...
    Still, I am using size 6.5 and Im thinking maybe to switch to a 6. If I would use a size 8 I could add a pair of oars and row across the ocean to the UK :)
     
  20. dg626

    dg626 Member

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    Same here in regards to the Vass Thread. I have decided on the Vass Shoes I want, and will probably place my order tomorrow. Bit of gamble in regards to size as I have no way of trying them, but hopefully I will get it right, and will report back in a few weeks when I get them.

    In regards to Carmina, thanks for posting your size. So looks like Size 7 should work for me in Rain, so I'm guessing maybe size 7 or 7.5 in Simpson last as I've read it's narrower than Rain.
     

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