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# Re: Wire gauge calc?

```David,

Here's a post from Alfred replying to Antonio on 4/29/98 (one I
held onto):
Bart

Antonio, I also worked on the relationship between the AWG (B&S)
gauge and
wire diameter back around 1991 while working on a program dealing
with
wire gauges I analized the relationship between B&S wire gauges
and the
wire diameter in inches and arived at an equation to calculate
the wire
gauge given the wire diameter, thereby eliminating the need to
include the
values in a large data statement area.

Even though it may seem unnecessary to use calculations acurate
to 15
decimal places, the fact is that if you were to round off to just
14
decimal places the equation will start to generate noticable
errors! As the
equation is it will give answers that perfectly match the
official
B&S wire tables as found in the CRC handbook of Chemistry and
Physics, the
Machinist's Handbook, and the Radio Amature Handbook by the ARRL.

Given the wire diameter d in inches, the B&S wire gauge = the
integer of;

-8.624487202999999 * natural LOG(d / .3245574964)

and if the resultant gauge is less than 1 make gauge = gauge - 1
to correct
for 0 gauges, ie. 0 gauge would be -1, 00 gauge would be -2, ect.

NOTE: even though this equation will give results like 000000
gauge and
larger at one extreme and 60 and smaller at the other, the
official AWG
(B&S) wire gauge starts at 00000 and ends with #40 gauge
respectively.

Given the AWG (B&S) wire gauge you can calculate the diameter of
the wire
in inches;

d = .3245574964 * 2.718281829 ^ (gauge / -8.624487202999999)

(you may notice 2.718281829 is e or the base of natural
logarithms) If the
gauge is less than 1 (the 0 gauges) then make gauge = gauge + 1

NOTE: when entering the 0 gauges (0,00,000,ect you would enter a
-1, -2, or
-3 respectively.

Then to calculate the various wire values ie. feet per pound,
feet per ohm,
fusing current, ect. I use;

turns per inch = 1 / d
diameter in mils m = d * 1000
cross-sectional area in circular mils = m ^ 2
cross-sectional area in sq. inches a = ((d / 2) ^ 2) *
3.141592654
feet per pound = 1 / (a * 3.853790614)
feet per Ohm = a * 122743.6823
fusing current for copper wire = 10244 * d ^ 1.5

Tesla List wrote:

> Original Poster: "David Knaack" <dknaack-at-idworld-dot-net>
>
> I used to have a calculation to convert AWG<->Inches, but
> I lost it, anyone know what it is?
>
> My wire is 11 mils in diameter, including insulation, but the
> spreadsheet wants it in gauge.
>
> Thanks!
> DK

```