Measuring Hair Thickness...and why your number might be wrong

**divinedobbie** · April 26th, 2014, 11:46 AM

I have been cursed with a little 2.5" ponytail circumference. I keep hoping that my tape measure is lying to me or that my hair will get thicker as I take better care of it so I measure it obsessively every month. Well it's been 8 months since I had extensions (I lost a lot of hair!) and about a year since I've started growing out my bangs. I figure that all my new growth should be about 4" long and my bangs about 6". Maybe all those short hairs just aren't getting into that one ponytail on top of my head and it's giving me a smaller number than it should be.

Someone recommended a really great idea in another thread. Divide your hair into two ponytails so that it gets all your shorter hairs, measure each ponytail separately, add the two numbers, and voila you have your real thickness!

After doing that, I got a 2" circumference for one ponytail and just over 1.5" on the second...which means I have a 3.5" circumference! Oh, I was so excited and in hair heaven!!

WRONG.

After my initial euphoria wore off, I started thinking about how that's even impossible. I can't put my finger on it exactly but I remember something about being able to increase surface area but still have the same volume. I repeated the tests by continuing to divide my hair into more sections, and sure enough, the overall circumference kept increasing.

Sadly enough, that means I still have a 2.5" ponytail. And unfortunately according to my theory, some of you who might have been measuring your hair and bangs separately, actually have a false number.

So am I right? And is there a way or formula to be able to measure my hair in two ponytails but still get an accurate overall circumference?

**Tall Blond(ish)** · April 26th, 2014, 12:11 PM

I won't bore you with the math details, but your conclusion is correct.

**ExpectoPatronum** · April 26th, 2014, 12:23 PM

This is why I don't measure my bangs separately. What I do is measure one ponytail without my bangs and then make another ponytail higher up to include my bangs. I take both those measurements and take the average. It may not be super accurate, but it at least accounts for my bangs.

**Seeshami** · April 26th, 2014, 12:24 PM

I never thought to include my bangs in my pony tail...

**darklyndsea** · April 26th, 2014, 12:38 PM

If you want to get your true circumference from two or more ponytails, you have to do math.

Measure your ponytails' circumferences. Write each down separately (don't add them together). circumference=2*pi*r; solve for r: r= C/(2*pi). area=pi*r*r. Add the areas together. find the radius of that area: sqrt(area/pi). Use that radius to find the circumference: C=2*pi*r.

**jeanniet** · April 26th, 2014, 01:26 PM

Don't get hung up on measuring thickness. If it gets significantly thicker, you'll know. If you must measure, just use a circle with your thumb and forefinger. It's reasonably accurate but doesn't give you a number to obsess over--and again, if your thickness increases, you'll know.

**LongHairLesbian** · April 26th, 2014, 02:29 PM

What's wrong with having a 2.5 inch pony? Bigger doesn't mean better, your hair is lovely and grows nicely as it is, it doesn't need to be any thicker to be beautiful.

I'll admit to being a bit obsessive about my hair's thickness; I'm guessing it's somewhere in the ii range, but I won't actually measure it, because I don't want to let a number define how confident I am or am not about my hair. You have beautiful hair, you don't need to change a thing.

**lapushka** · April 26th, 2014, 03:08 PM

Originally Posted by LongHairLesbian

What's wrong with having a 2.5 inch pony? Bigger doesn't mean better, your hair is lovely and grows nicely as it is, it doesn't need to be any thicker to be beautiful.

I'll admit to being a bit obsessive about my hair's thickness; I'm guessing it's somewhere in the ii range, but I won't actually measure it, because I don't want to let a number define how confident I am or am not about my hair. You have beautiful hair, you don't need to change a thing.

Totally agreeing with this. What's this "obsession" with thick hair, anyway. It's not all that great over on this side (iii), you know.

**jeanniet** · April 26th, 2014, 03:27 PM

Originally Posted by LongHairLesbian

What's wrong with having a 2.5 inch pony? Bigger doesn't mean better, your hair is lovely and grows nicely as it is, it doesn't need to be any thicker to be beautiful.

I'll admit to being a bit obsessive about my hair's thickness; I'm guessing it's somewhere in the ii range, but I won't actually measure it, because I don't want to let a number define how confident I am or am not about my hair. You have beautiful hair, you don't need to change a thing.

Not a thing. I think i hair is beautiful, as is ii. iii hair is quite often a PITA, and IMO doesn't look any better (especially on a windy day). I guess it's easy for me to say, since I have iii hair, but if the people with i/ii knew how much I fought and despaired over this much hair for most of my life...! It's better now because I've learned to work with it instead of trying to control it, but it will never, ever be tamed.

**kaydana** · April 26th, 2014, 03:28 PM

Originally Posted by darklyndsea

If you want to get your true circumference from two or more ponytails, you have to do math.

Measure your ponytails' circumferences. Write each down separately (don't add them together). circumference=2*pi*r; solve for r: r= C/(2*pi). area=pi*r*r. Add the areas together. find the radius of that area: sqrt(area/pi). Use that radius to find the circumference: C=2*pi*r.

This is correct, but there's no need to do quite that much work. It simplifies down to

c = sqrt(a^2 + b^2)

Where a and b are the two measured circumferences, and c is the total circumference of all the hair.

So, in this case:

c = sqrt(2^2 + 1.5^2)
c = 2.5

Still 2.5" I'm afraid, which is to be expected really, because half inches aren't nearly precise enough for the kinds of increases you'll get measuring in two ponytails rather than one.