Talk:Circular mil

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In what way is a value given in circular mil "not the true cross sectional area" - is the cross sectional area of a wire whose area is given as 4 circular mils something other than 2.0683·10-9 m3? Or is this trying to say that it's sometimes used without being specified (so that people might think some other unit of area is being used)?--Random832 (contribs) 20:05, 16 April 2008 (UTC)

This article is awful! It is written from the point of view of someone who hates circular mils, like that is convenient or useful in an encyclopedia. Needs a rewrite. I like to saw logs! (talk) 07:00, 3 May 2008 (UTC)

I've modified the equivalent in square milimeters as it was off by a factor of 1,000. I've also removed the word convenient as there is nothing convenient about this cumbersome archaic and arbitrary system. —Preceding unsigned comment added by 62.94.33.30 (talk) 14:50, 21 November 2008 (UTC)

NOT CONVENIENT
Its not a convenient unit. Use metric units (mm2)!! — Preceding unsigned comment added by 150.227.15.253 (talk) 09:12, 22 August 2013 (UTC)
 * I'm tempted to simply change the word to "inconvenient", but an actual neutral wording is probably for the best. EBusiness (talk) 15:06, 19 May 2014 (UTC)

cmil to square inches
This formulas can't possibly be right in its current form: "circular mil = square inches × π ÷ 4,000,000". Plugging in 0.7854 millionths of a square inch (as this is the value given in the next section "1 circular mil is approximately equal to: 0.7854 millionths of a square inch (1 square inch is about 1.273 million circular mils)") does not result in 1 cmil! Reversing it to "circular mil = square inches ÷ π × 4,000,000" fixes it. I have done so. —Preceding unsigned comment added by 66.161.180.226 (talk) 18:55, 19 November 2009 (UTC)

is this right?
Circular Mills Explained What are Circular Mils?

There are many different wire gauge systems used to specify electrical wire size. In North America the two most common systems are the SAE (Society of Automotive Engineers) and AWG (American Wire Gauge). A 14 SAE wire is smaller than a 14 AWG wire and therefore, for a given insulation temperature rating, capable of carrying less electrical current.

In many ABYC tables and wire suppliers catalogs the cryptic term "Circular Mils" will be shown as part of the wire specification. Circular Mils is the term created for the measurement system devised to measure wire conductor (without the insulation) sizes in absolute terms. By specifying how many Circular Mils a 14 SAE wire has compared to the Circular Mils in a 14 AWG wire it is possible to determine the relative amounts of copper in each wire.

Unfortunately the term Circular Mils does little to clarify the situation for the average person because it is a unit of measure not used commonly and it doesn't necessarily have anything to do with circles!

One Circular Mil is a unit of area equal to that of a circle .001" in diameter (.0005" radius). The actual area of a Circular Mil is:

A =Pi x r²

A = 3.14159 x (.0005)² inches

A = .0000007857 square inches

When wires get very large their sizes are sometimes shown as "MCM", such as 250MCM. MCM means Thousand (M) Circular (C) Mils (M). A 250MCM wire is wire with an area equal to 250 x 1000 Circular Mils

The illustrations show that a circle can be 1 Circular Mil, but a square can be one too!

A = .0000007857 square inches / A = .0000007857 square inches

These are both 1 Circular Mil! —Preceding unsigned comment added by 75.158.120.21 (talk) 03:46, 4 November 2010 (UTC)

Why this category?
I added category decimalization to cover subject related to introduction fractions of 10 for subunits of various measurements, see category description. This article is part of the "mil" topic. As you know, mil is 1/1000 of inch. As youy know, categories are to keep related topics together, for easy browsing. Loew Galitz (talk) 23:31, 22 November 2011 (UTC)
 * Wouldn't it make more sense to reserve the category for things that converted previously non-power-of-ten measures to power-of-ten measures? Everything is measured in base 10 so everything can be in "decimalization". --Wtshymanski (talk) 03:02, 23 November 2011 (UTC)

It took years
It took years and a number of re-writes, but at last this article is stable. But more importantly, it is accurate and the formulae presented can be used without causing a conniption fit in the many IP-based editors who see them for the first time. I don't know how many times I had to revert the formulae, but I seriously doubted whether I was correct many times until I brought in the AWG formula to prove it. Hopefully this will put to rest any of the arguments on conversion amongst various units. I like to saw logs! (talk) 08:15, 22 January 2012 (UTC)


 * Please, editors, read this!! (Written 3 years later)


 * This article stabilized by correcting the many errors and using plain math, true enough... but mainly by taking the time to fully understand the topic. If it is still confusing, you need further study. Work some problems out. Go through the examples forward and backwards. It didn't make complete sense for some of us on the first read through. This unit is very different from other units of area. That makes it peculiar, but not exactly difficult to understand.


 * The reader may need some hand-holding to ensure he follows it. I have done this by repeating the crucial but mundane calculations of area, with an emphasis on wire sizes and diameters. The idea of a radius need not be mentioned; however, the NEC and the old-time table lookups are essential, as the circular mil was traditionally used in table lookups from simple calculations, prior to handheld electronic calculators. The diameter of a circular wire is measurable in the field, and its area in circular mils is calculable with pencil and paper in the field. Its simplicity is apparently lost on those who have a singular understanding of a circular cross-section, but not if you consider its use by those who were traditionally less educated tradesmen: electricians. So do not let the simplicity of the unit fool you: be extra careful in unit analysis and conversions or you will start another "This is Confusing" section on this Talk Page! I like to saw logs! (talk) 04:44, 25 January 2015 (UTC)

Suggest merge
Is there any field that uses "square mils"? If it's only used in calculations of wire area, all the trivial grade-school arithmetic is already adequately explained here and there sems little need for a separate article on an unused unit of measure. --Wtshymanski (talk) 14:31, 26 September 2012 (UTC)

very confusing
I was unsure, and after reading this article I am confused. The only unclear point, from my perspective, is: "A circular mil has a circle area or not?" The article says Π (PI, 3.14159..etc.) is not involved. Then, I find online calculators where circular mil is not the same as square mil, and the circular mil is calculated as a circle area. Are online calculators wrong? Is the word "circular mil" used to refer to different standards, in different situations? I think this argument need some clarification. — Preceding unsigned comment added by 88.149.241.119 (talk) 18:05, 3 May 2013 (UTC)
 * IMHO there are no different standards, but it is you who refers to different meanings in different contexts. The article does not say whether π is involved or no, it only gives a (numeric) formula for the area/diameter dependence. Circular mil is a unit of area. A quantity is a unit multiplied to a number. Quantities are not numbers. Recall the squaring the circle formula, try to meditate about this, and you will understand the puzzle. Incnis Mrsi (talk) 19:47, 3 May 2013 (UTC)

You are right. "Circular mil" should be read as "Wire section unit", nothing more. The confusing part is the name of the unit (circular mil) containing the name of another, mathematically uncorrelated unit (mil). — Preceding unsigned comment added by RickyGold (talk • contribs) 01:31, 4 May 2013 (UTC)
 * I do not see anything confusing at all, at least for me. You learned in the school that the area is measured in “square … ” units, which are equal to area of a the square with specified side; this is the prevailing convention for area in our civilization. From mathematical point of view, the area is well defined, but the square is not an exceptional or only possible shape to serve as a unit. Many formulae become simpler if you use the 1-1-√2 right triangle as the unit, a half of unit square (or, more generally, the standard simplex for n-dimensional space, which has $1⁄n!$ of the measure of the unit hypercube). An alien from the Plane of Discs and Ellipses, where polygons do not occur, certainly will see “your” square unit as a jarring transcendental factor in the formula for the area of a basic shape. I would not say anything like mathematically uncorrelated unit about this case. It is you whose mind rejects the word “ circular ” as a semantic parallel to “square”. Incnis Mrsi (talk) 04:58, 4 May 2013 (UTC)

there is a mistake in calculation it should be as follows: 211600 circular mils = 52900 x 3.14 [pi]

1 circular mil= 52900 x 3.14 [ pi]/211600 = 3.14[pi]/4

and hence 1 sq.mil= 4/3.14[pi] cm — Preceding unsigned comment added by 117.203.111.24 (talk) 10:35, 10 June 2013 (UTC)


 * You are right. Someone keeps editing these formulae and messing them up, so I fixed them! I like to saw logs! (talk) 06:00, 18 June 2013 (UTC)

Craigde (talk) 15:37, 24 January 2015 (UTC)
 * On 1/24/2015 the very first sentence, "A circular mil is a unit of area, equal to the area of a circle with a diameter of one mil," is wrong. This might explain something.


 * No, you are confused. I am one of very few people who edit this article and attempt to make sense of it. It took quite a bit of thought, but was correct before you changed it. The statement is correct and it guides the reader to what may seem to be a paradox: the area of a circle with a diameter of one mil can be given in at least two different units. The circular mil value is exactly one ... the square mil value, which uses the formula you have become accustomed to, is π/4. So the article needs to lead with this statement, not your edited statement with the 4/π value.

"A circular mil is a unit of area, equal to the area of a circle with a diameter of one mil (one thousandth of an inch)."


 * This 4/π parameter can appear later, once the terms are defined and necessary to the discussion, but not in the lead sentence. [It does appear later, by the way, already.] I also noted that using square mils, a practically unheard of unit of area, should not appear in the lead sentence. I am going to make a note in the article this time, to perhaps prevent (a common?) misunderstanding. I like to saw logs! (talk) 03:59, 25 January 2015 (UTC)

A Commons file used on this page or its Wikidata item has been nominated for deletion
The following Wikimedia Commons file used on this page or its Wikidata item has been nominated for deletion: Participate in the deletion discussion at the. —Community Tech bot (talk) 21:37, 12 July 2022 (UTC)
 * Gauge Chart.pdf

Relation to Specific Electrical Resistance

 * Currently in electrical in some sections this unit has been mentioned/covered
 * The formula they used for the resistance of a conductor for instance is:
 * Rohms = K × 2Lfeet / ACM Where K (or Kappa i guess) is The Specific Electrical Resistance of the material (Copper Wire, Aluminum Wire, Single vs Multistranded etc), L is the Length of the Conductor, and A is the area in Circular Mils
 * CM (Somewhat) Confusingly standing for Circular Mils, not Centimeters
 * Just thought this may be a good addition later and/or have the "See Also" section link to a page on all this

Eric Lotze (talk) 16:21, 25 January 2023 (UTC)