EXACT MEASUREMENT!!

[new guy]

What is the EXACT length conversion of 1 millimeter to inches. There are alot of different answers out there??

[ku7485]

Is this exact enough for your purposes?

1 millimeter = 0.0393700787 inches

or 5/127 inches.

[HighFrequency]

there are EXACTLY 2.54 cm in one inch

[ku7485]

there are EXACTLY 2.54 cm in one inch

Yep, same thing as mine.

2.54 x 10 = 25.4mm

1/25.4 = 5/127

5/127 inches in a millimeter.

[dyarker]

Yeap, NIST says 1 inch is exactly 2.54cm; which would be 25.4mm per inch.

1/25.4 = 0.03937007874015748031496062992126 inches per mm.

I suspect the calculator ran out of digits at the six on right. To check if it is exactly 1/25.4, you'd use long division and see if the remainder is zero at that digit.

Any answers different than 25.4 or 0.03937... are wrong (2.54cm/in is the international agreement).

Cheers,

[MrAl]

Hi there,

Guess what?

Here is the number 1/25.4 shown in 25 groups of 7 digits:

0.0393700,7874015,7480314,9606299,2125984,2519685,0393700,
7874015,7480314,9606299,2125984,2519685,0393700,7874015,
7480314,9606299,2125984,2519685,0393700,7874015,7480314,
9606299,2125984,2519685,0393701

Look closely...see anything interesting?

I'll repeat the above number but arrange it a little better:

0.0393700,7874015,7480314,9606299,2125984,2519685,
0393700,7874015,7480314,9606299,2125984,2519685,
0393700,7874015,7480314,9606299,2125984,2519685,
0393700,7874015,7480314,9606299,2125984,2519685,
0393701

Now see it? ha ha... it's a repeating decimal!
The digits repeat every 42nd digit, forever!
Note the last "0393701" is the remainder of the number rounded up,
but it actually repeats those 42 digits again.

[HighFrequency]

Good catch Al. You have too much time on your hands.

[MrAl]

HI again,

Ha ha, what happened was i didnt use my big number program for
a while now so i decided to do a quick calculation using it.
I noticed the repeating decimal so i posted it here.
I never realized that 1/25.4 was a repeater before this.
I guess that's because most calculators only go up to 16 or 32 digits,
and you dont see the repeat until after the 42nd digit.

To be practical i guess this wont affect any calculations i will be doing
anytime soon anyway though, because i use 16 digits for most
things and even then the result is truncated.

[willbravo]

Lord Rightbrain here. It may be mentioned elsewhere, but google's calculator is one of the most convenient tools I've found for this kind of thing. BUT my question is, "What do you mean by 'a lot' of different answers?" Are you saying that you've run into a lot of people using the same formula and getting a different answer? Or are you saying you've seen a lot of different conversion formulae?

I'm the newest of new, and already lovin' this place!
Cheers!

What is the EXACT length conversion of 1 millimeter to inches. There are alot of different answers out there??

[bwts]

strange i always thought it was 2.541 cm to an inch

[MrAl]

Well, the actual original question was not how many millimeters to the
inch, but was this:

What is the EXACT length conversion of 1 millimeter to inches. There are alot of different answers out there??

In other words, convert 1mm to inches, period. This is not possible
to do EXACTLY, because the conversion results in a fraction that
has a repeating decimal as i showed earlier in this thread...

1mm=
0.0393700,7874015,7480314,9606299,2125984,2519685,
0393700,7874015,7480314,9606299,2125984,2519685,
0393700,7874015,7480314,9606299,2125984,2519685,
0393700,7874015,7480314,9606299,2125984,2519685,
0393701 inches,
but keep in mind that the last 0393701 is the actual remaining
digits rounded up, and really the numbers keep repeating indefinitely.
This makes the number unable to be converted exactly. In other
words, there is no exact conversion.

We can represent the number as the ratio of two integers:
1mm=10/254 inches,
but that doesnt do us much good.

[bwts]

Maybe the solution is to convert completely to the metric system. Resistance is futile.