Measuring Circumference

[zetwal]

I just pulled these quotes from a couple other threads.

A way I've used is to measure the size is around the outer crown then subtract an inch.

I put it out to fellow loungers: will those people out there who have a fabric tape reproduce my method and see if the results are consistent - does the outer tape measurement minus 1 inch give the correct hat size for your inventory?

Does anyone else use THIS method? Has anyone else even tried it? If so, how reliable are the results for you? If you haven't yet tried THIS particular method, please do so with your own hats. Then report here what you find when you do it. Thanks!

 

[rlk]

Gauss-Langenberg Measure

 

[zetwal]

Exactly!

 

[rlk]

Of course this works for an "average" thickness sweatband,felt and hatband. Its still probably better than the average persons'(certainly ebay sellers ) inner circumference measuring attempts...

 

[ScottF]

Exactly!

Hey - you guys are geniuses! This is going to save a lot of time and add accuracy - thanks.

 

[Wolfmanjack]

This is the question I have tried with eBay sellers:

The actual size of a hat can vary widely from the stated size, due to shrinkage, etc. To be sure, it is best to take a direct measurement around the inside sweatband of the hat. You can use a belt to measure the inside circumference of the hat. Roll up the belt, place it inside the hat, unroll it until it is snug against the sweatband all around, and then mark the belt where the two ends overlap. Unroll and measure the distance between the two marks with whatever you have handy, e.g., a yardstick.​

Unfortunately, most sellers were baffled by these instructions, so now I just ask this:

Can you please measure the inside diameter of the hat from front-to-back and side-to-side?​

.
Then I use this ellipse circumference calculator to determine the inside circumference of the hat. This works (sometimes) for me.

When one measures around the outside of the crown where it meets the brim, I would think errors can occur due to variations in the thickness of the ribbon and bow. Also, I would expect that using this technique on a reeded sweatband would result in an over-estimation of the hat size.

Just my opinion.

 

[galopede]

I use a length of masking tape, don't know if you call it that in the States. A paper based, cream coloured sticky tape they use in decorating with very little stickiness. Peels off after they've painted leaving a clean line.

Anyway, I stick that around the inside band, cut it exact length or use a marker, peel off and measure.

Exact!

Gareth

 

[Wolfmanjack]

A math lesson from the old professor

I just pulled these quotes from a couple other threads.

Quote:
Originally Posted by J.J. Gittes
A way I've used is to measure the size is around the outer crown then subtract an inch.

Quote:
Originally Posted by carldelo
I put it out to fellow loungers: will those people out there who have a fabric tape reproduce my method and see if the results are consistent - does the outer tape measurement minus 1 inch give the correct hat size for your inventory?

Does anyone else use THIS method? Has anyone else even tried it? If so, how reliable are the results for you? If you haven't yet tried THIS particular method, please do so with your own hats. Then report here what you find when you do it. Thanks!

When you increase the circumference of a circle by 1 inch, you increase the diameter by 1/pi or 0.318 inches (or about 5/16 of an inch).

(Of course I know the inside of a hat is an ellipse, not a circle; but let’s keep things simple.)

When you estimate the inner circumference around the sweat of a hat as one inch less than the outer circumference around the crown at the ribbon, you are assuming that the thickness of the sweat, the reed, the liner, the felt, the ribbon bow, and maybe a feather, all add up to exactly 0.318 inches.

If this assumption is wrong by as little as 1/8 of an inch, you make an error of one full hat size.

 

[Wolfmanjack]

I use a length of masking tape, don't know if you call it that in the States. A paper based, cream coloured sticky tape they use in decorating with very little stickiness. Peels off after they've painted leaving a clean line.

Anyway, I stick that around the inside band, cut it exact length or use a marker, peel off and measure.

Exact!

Gareth

That is brilliant, Gareth!

BTW, A belated welcome to the FL.

 

[rlk]

The biggest problem with all internal measurements is measuring at the correct point of the opening, not down to the middle of the sweatband or to the outside edge of the leather. This can result in a 2-3 size error. The thickness factors in twice for the diameter so actually.158" a little over 1/8". The bow /feather etc. do not wrap all the way around so barely have an effect on the circumference. The exterior base of crown measurement is very easily(almost automatically) done at the correct point with reasonable accuracy.

 

[Wolfmanjack]

1/8" off on the thickness of the materials is an error in measurement of nearly 40 percent so highly unlikely.

rlk, The thickness of the materials is not something one would measure; it is an assumption upon which the calculation is based. The assumption is that the average thickness of the materials is exactly 1/pi or 0.318 inches.

If one were to actually try to make the measurement, they would have to measure the thickness of the materials at a large number of points around the hat, then take the average of these. The likelihood of error would be quite large.

 

[rlk]

rlk, The thickness of the materials is not something one would measure; it is an assumption upon which the calculation is based. The assumption is that the average thickness of the materials is exactly 1/pi or 0.318 inches.

If one were to actually try to make the measurement, they would have to measure the thickness of the materials at a large number of points around the hat, then take the average of these. The likelihood of error would be quite large.

As I added to the above, the feather/bow only wrap a very small portion of the hat so their variation has a truly small effect on the overall circumference. Not in any way suggesting taking a calipers to measure thickness which would be more accurate as you average more measurements...but how much variation in the thickness would be required to create a significant size error. Also, the reed sits below the brim and is not involved, nor does the liner reach that point, so basically it is only the felt and the leather thickness at this point which corresponds to the heads widest point. So, without an expanding measurement device or the knowledge of the correct measuring points it is likely one of the closer methods for the inexperienced.

 

[carldelo]

rlk, The thickness of the materials is not something one would measure; it is an assumption upon which the calculation is based. The assumption is that the average thickness of the materials is exactly 1/pi or 0.318 inches.

If one were to actually try to make the measurement, they would have to measure the thickness of the materials at a large number of points around the hat, then take the average of these. The likelihood of error would be quite large.

RLK is correct, the difference of 0.318 must be split, as the 1/Pi difference is between the inside and outside diameters of the hat. The tacit assumption therefore is that the material thickness is about 0.16 inch on average - possibly a little different as the shape is not circular.

All of Wolfman's arguments above are correct, yet I agree with RLK - the bow is not a significant issue as it takes up a relatively small portion of the circumference, and the outside measuring tape tends to squash it down, reducing the effect.

In addition, the error analysis in this method is somewhat subtle, best shown via example - check me, as I think this is right, but am not 100% sure.

e.g. I measure the outside circumference of my Chatham and get 25-3/8". This corresponds to an outside diameter of 8.07". If I subtract twice the thickness (.32") this give 7.75" which is 7-3/4, the true size of the hat.

If the felt+sweat happens to actually be 50% thicker (.24", a big jump) then subtracting twice the thickness (.48") gives 7.59, or just under 7-5/8. So the estimate of 7-3/4 would be one size bigger than the actual size of the thick hat.

If the felt+sweat is actually 50% thinner than assumed (.08") then the size of the hat is 7-7/8, and the estimate of 7-3/4 is one size too small​

So the thickness assumption is pretty good overall (to an engineering approximation, within one size) and is the source of the 'subtract one inch from outside measurement' method. I think it's because, in reality, the thickness of felt and sweatband is fairly consistent overall. As a method, I believe it certainly rivals the 'length by width' method, or trying to get clueless ebayers to measure an inside circumference.

My final argument is experimental - i.e. I tested the method on all 12 of my hats, and it worked extremely well, accurately giving the sizes. I measured vintage and modern fur felts, a straw, a poly and a couple of fabric fedoras. As far as I know, no one else on the FL has systematically gone through their hats to try this out, so I believe that gives me the last word on the subject - lol - and yes, I realize that is a ridiculous statement in the extreme....

 

[CRH]

...As far as I know, no one else on the FL has systematically gone through their hats to try this out, so I believe that gives me the last word on the subject - lol ...

Carldelo had collected the data. I'm sitting with him on this question so far.

 

[Landman]

Ellipse Circumference Calculator

Below is a link to a very handy calculator for hat collectors. I'm not associated in anyway with this calculator or website. I just thought some of you might find it helpful. It is great for getting a rough estimate of the inner circumference of a hat that has lost it's size tag. I tried it out on a couple of my hats with known sizes and it was very accurate.

http://www.csgnetwork.com/circumellipse.html

 

[randooch]

Thanks for this, Landman. I often want to post a link to one of these calculators in my ebay listings, and this will be the one.

 

[Landman]

No problem. I tried it on one of my VS hats with a known circumference and it was dead on.