Watch size formula

[Adeodatus]

We almost always buy watches online and sometimes upon receiving the watch you realize it is too big for your wrist or too small. Knowing the diameter works well enough, but we all have different wrists of different shapes, so I've been thinking of a more (pseudo) scientific way to tell if the watch you are buying will fit your wrist.

This is what I've been thinking about:

j=a/b

a = your wrist perimeter

b = your wrist width

j = your wrist constant

k=(x+((y-x)/2))/2

x = watch diameter

y = watch width including the lugs

k = your watch constant

Q=j/k

0.12<Q<0.15 - the watch is right for you

Q<0.12 - the watch is too large for your wrist

Q>0.15 - the watch is too small for your wrist

I've tried this formula with a few watches I have and it seems to work. Can you please help me verify this (if you are interested of course).

Man... I have too much free time on my hands

[seeaye]

why do you think that k should be that? rather than just y/x or x/y.. would just give you a different normal range for Q?

great thought though I like the way u think

[ninjagaiden]

I would try and squeeze a PI in there somewhere, given that wrist perimeter and wrist surface are related!

Of course, you would need to perform a regression analysis of your formula by being given hundreds of different gen watches to try out and see how well they conform to your formula.

Then, to validate your regression analysis, you would need to be given hundreds of rep watches and repeat the exercise.

Man - I feel a grant application coming along.

<tongue firmly in cheek>

N

[Bardamu]

I'm not sure that we can define a formula that could calculate accurately if the size of the watch will fit with our wrist. Your formula is a good start, but you cannot be sure before you try it on. Other points, more difficult to estimate, have to be taken into account. I have two points in mind :

- Do you use to wear large watches or not ? This will be important to decide if you feel comfortable or not with it.

- What is the weight and thickness of the watch ? This point can be important. A large and flat watch can be wore easily. But if the same case is very thick and heavy (diver watch like DSSD, for instance), you will feel it very different. Each time you move your hand, the watch move much more than a flat one.

So, at the end of the story, I would say that my personal formula would be "you like it ? take it ! "

Paul

PS : I just see that this is my 69th post. Coooooooooooooool !

Edited January 18, 2012 by Bardamu

[Adeodatus]

... given hundreds of different gen watches to try out ..

Then... you would need to be given hundreds of rep watches..

Damn, I like the sound of it!

[Adeodatus]

I'm not sure that we can define a formula that could calculate accurately if the size of the watch will fit with our wrist. Your formula is a good start, but you cannot be sure before you try it on. Other points, more difficult to estimate, have to be taken into account. I have two points in mind :

- Do you use to wear large watches or not ? This will be important to decide if you feel comfortable or not with it.

- What is the weight and thickness of the watch ? This point can be important. A large and flat watch can be wore easily. But if the same case is very thick and heavy (diver watch like DSSD, for instance), you will feel it very different. Each time you move your hand, the watch move much more than a flat one.

So, at the end of the story, I would say that my personal formula would be "you like it ? take it ! "

Paul

Absolutely, I need to add +/- 0.01 for "likability"

[Jmabshir]

Pretty interesting, I calculated and found that for most of my watches i'm at either of the boundaries you have exactly (.12 and .15) with the PAM111 at Q=.12.

[TeeJay]

I'm no good with math, but I really like that idea

[Ronin]

Please clarify your terminology.

What is a wrist perimeter? Width? I think I know what you mean, but it is a bit unclear. You also mention watch width with lugs, so I assume you are talking about a 12-6 'length' measurement and not a 9-3 'width' measurement. Should crown width be considered?

Put this into an Excel spreadsheet once we shore up the definitions.

[Adeodatus]

Perimeter is the wrist size ie 7", 6 1/2" etc in mm

Wrist width is the actual width of your wrist

The watch width is indeed the 12-6 measurment

Here is the excel

watch_size_formula.xls

[Ronin]

Excellent. The Excel Spreadsheet worked great. Proved what I already knew, that Rolex 40mm watches are perfect for me.

[wiesn089]

Thanks, that's very interesting! I checked some watches and it seems to be almost spot on for me. I adjusted the values a little bit to fit my taste (<0.13 too large) since a Speedmaster is about the biggest I am comfortable to go and it sits at 0.13, but that's about it, great work, thanks!

[frankt]

Dial size vs overall case size needs to be considered also...For instance compare a Big Pilot to a Ploprof to see what I mean!!

[Ronin]

Other Variables:

-Dial Color (White wears Bigger, Black wears smaller)

-Case Thickness (Thicker / Top heavy wear bigger. Slimmer (on a large diameter) wear smaller)

[Adeodatus]

You're probably right, Ronin. The only question is how to sum it up mathematically, especialy the colour.

[Nanuq]

This is fine pre-purchase. For post-purchase empirical analysis, I believe one can make the observation that

WD ~ k•(1/[Mp])

where WD is watch diameter, k is a constant and Mp is phallic mass.

[RobT]

wow, surprised someone came up with a formula! Ill give it a try

[OldCorvette]

Unfortunately, computing this formula sounds like the perfect job for.... the Casio Data Bank !!

Seriously, If you:

1. Know the width of your wrist in Millimeters

2. Find the Lug to Lug width specs and case diameter specs of the watch you are considering

You're at 95% of this formula without relying on a Casio.

Edited January 27, 2012 by OldCorvette

[alexfilipov]

This formula is indeed ingenious and works for me. Tested it on all my watches. Million thanks! Now I know I need a 42 mm Omega PO

[Adeodatus]

Great! Glad you find it useful, mate.

Get that PO, you won't regret it.

[SlipperyPete]

What's the best way to find the lug to lug width? Say, I'm deciding between a 42mm & 45.5mm Planet Ocean, how can I find the width? This would be a sweet online calculator if there was a database with watch specs!

[Adeodatus]

Omega PO 42 lug to lug size: 47.7 mm

Omega PO 45.5 lug to lug size: 52mm

[horolophile]

Alas there's a problem with the math here:

 

Imagine for a moment your wrist was perfectly round.

 

Now, for the formula as stated:

 

a = circumference ( c )

b= diameter ( d )

 

j = circumference/diameter

 

Now, we know the classic 'c = 2πr', or alternately 'c = πd', which can be rearranged to 'c/d = π'.

 

So, were your wrist a perfect circle, j would *always* = π, no matter how big or small your wrist actually *is*.

 

Now, true, nobody's wrist is perfectly circular, but in measuring the equivalent of 'c/d' (in our case 'a/b') we are only measuring how 'out of true', or how 'flat' someones wrist is, and the resultant 'j' tells us nothing about the actual size of the wrist, which is kinda' important when determining watch size.

 

Just my 2¢

 

Pax

-Aaron

Edited February 19, 2013 by horolophile

[horolophile]

Alas there's a problem with the math here:

 

Imagine for a moment your wrist was perfectly round.

 

Now, for the formula as stated:

 

a = circumference ( c )

b= diameter ( d )

 

j = circumference/diameter

 

Now, we know the classic 'c = 2πr', or alternately 'c = πd', which can be rearranged to 'c/d = π'.

 

So, were your wrist a perfect circle, j would *always* = π, no matter how big or small your wrist actually *is*.

 

Now, true, nobody's wrist is perfectly circular, but in measuring the equivalent of 'c/d' (in our case 'a/b') we are only measuring how 'out of true', or how 'flat' someones wrist is, and the resultant 'j' tells us nothing about the actual size of the wrist, which is kinda' important when determining watch size.

 

Just my 2¢

 

Pax

-Aaron

 

Just as a quick example:

I've got big wrists, and (roughly) have a = 19.5, and b = 7, so my j = 2.79.

Meanwhile, my daughter has a = 17.25, and b = 5.75, so her j = 3.00.

 

Now, to compare to one of the watches above (the 45.5mm Planet Ocean, since I have one to test with) which ends up having k = 24.38 once you crunch the numbers.

 

For me, 2.86/24.38 = .11, so this watch is too big for me (according to the formula)

For my daughter, 3.00/24.38 = .12, so the same watch fits her significantly smaller wrists (again, according to the formula).

 

Having just tried the watch on, and then having her try it on, I assure you, it looks just about perfectly sized on me and laughably large on her.

[martijnp]

Perimeter is the wrist size ie 7", 6 1/2" etc in mm

Wrist width is the actual width of your wrist

The watch width is indeed the 12-6 measurment

Here is the excel

 

Thanks that just looks great! Will try it when I'm back home