AWG NEMA / IEC Metric Standard Size Chart - Bare Wire Dimensions -

AWG (American Wire Gauge)

AWG numbers follow a mathematical formulation devised by Brown and Sharpe in 1855. The AWG designation corresponds to the number of steps by which the wire is drawn. (18 AWG is smaller than 10 AWG, therefore is drawn more times to obtain a smaller cross sectional area.) According to the "Standard Handbook for Electrical Engineers" (Fink and Beaty) 'gauge' is the American Wire Gauge also known as the Brown & Sharpe gauge, which is the standard for which American engineers adhere.
AWG began at 4/0 wire with a diameter of 0.46" and the next lower wire size was derived by multiplying the diameter by 0.890526. These then became tabulated into what we today call the AWG; ranging down to 40 gauge wire at 0.003" in diameter. The primary concern in a mechanical standard is for electrical conductors and current carrying capacity (driven by resistance).
To protect engineers from lawsuits and physical harm a resistance measurement system was implemented to certify that all wire produced in the United States met the DC resistance specifications. The process of measuring the DC resistance is known as the 2-terminal method.

 AWG SIZE NEMA Nominal Diameter Inches / MM IEC R-20 Series MM AWG SIZE NEMA Nominal Diameter Inches / MM IEC R-20 Series MM 4/0 0.4600 11.684 - 27 0.0142 0.361 0.355 3/0 0.4096 10.404 - 28 0.0126 0.320 0.315 2/0 0.3648 9.266 - 29 0.0113 0.287 0.280 1/0 0.3249 8.252 - 30 0.0100 0.254 0.250 1 0.2893 7.348 - 31 0.0089 0.226 0.224 2 0.2576 6.543 - 32 0.0080 0.203 0.200 3 0.2294 5.827 - 33 0.0071 0.180 0.180 4 0.2043 5.189 5.000 34 0.0063 0.160 0.160 5 0.1819 4.620 4.500 35 0.0056 0.142 0.140 6 0.1620 4.115 4.000 36 0.0050 0.127 0.125 7 0.1443 3.665 3.550 37 0.0045 0.114 0.112 8 0.1285 3.264 3.150 38 0.0040 0.102 0.100 9 0.1144 2.906 2.800 39 0.0035 0.089 0.090 10 0.1019 2.588 2.500 40 0.0031 0.079 0.080 11 0.0907 2.304 2.240 41 0.0028 0.071 0.071 12 0.0808 2.052 2.000 42 0.0025 0.064 0.063 13 0.0720 1.829 1.800 43 0.0022 0.056 0.056 14 0.0641 1.628 1.600 44 0.0020 0.051 0.050 15 0.0571 1.450 1.400 45 0.00176 0.0447 0.045 16 0.0508 1.290 1.250 46 0.00157 0.0399 0.040 17 0.0453 1.151 1.120 47 0.00140 0.0356 0.035 18 0.0403 1.024 1.000 48 0.00124 0.0315 0.031 19 0.0359 0.912 0.900 49 0.00111 0.0282 0.028 20 0.0320 0.813 0.800 50 0.00099 0.0251 0.025 21 0.0285 0.724 0.710 51 0.00088 0.0224 0.022 22 0.0253 0.643 0.630 52 0.00078 0.0198 0.020 23 0.0226 0.574 0.560 53 0.00070 0.0178 0.0187 24 0.0201 0.511 0.500 54 0.00062 0.0157 0.0157 25 0.0179 0.455 0.450 55 0.00055 0.0140 0.0140 26 0.0159 0.404 0.400 56 0.00049 0.0124 0.0124 AWG SIZE NEMA Nominal Diameter Inches / MM IEC R-20 Series MM AWG SIZE NEMA Nominal Diameter Inches / MM IEC R-20 Series MM

Although there is a world-wide trend to the International System (SI) or Metric measurement, the current practice in wire measurement in the United States is generally the use of the customary English Units. The current practice of the NAtional Bureau of Standards (NBS), the Institute of Electrical and Electronic Engineers (IEEE), and the The American Society of Testing Materials (ASTM) is to reflect American Wire Gauge in parallel with metric units of measurement.

The American Wire Gauge, like some other gauge systems, does generally represent steps in the wire drawing process. In addition to that, the numbers are retrogressive to the wire size -- that is, the larger the number the smaller the wire. These gauge sizes are not arbitrary, but are a geometric progression. With the definition of two sizes in the series of gauge sizes, all size related properties of any gauge in the series is defined by that relationship. With AWG 0000 as 0.4600 inch and AWG 36 as 0.0050 and 38 gauge sizes between these two, the ratio of any diameter to the next larger diameter can be determined as follows:

 = = 1.1229322

The square of this ratio is: 1.2610

This Square of the ratio between sizes can be used as a means of obtaining the resistance, mass and cross section of any wire size if one is memorized these values for only one size. This conversion number can easily remembered as 1 1/4.

Therefore:

Knowing 20 AWG has a cross-section of 1020 circular mils tell us 19 AWG will have 1 1/4 x 1020 or approximately 1250 circular mils. If we had memorized the resistance of 20 AWG as 10 ohms/1000 feet, 19 AWG would have less resistance by 10 ÷ 1 1/4 or approximately 8 ohms/1000 feet.

Since the function os geometric, the cube of this 1 1/4 is approximately 2. This allows you to easily calculate the dimensional functions in 3 gauge increments. Every 3 gauge sizes the resistance, mass per unit, and cross section will double or halve.

Then with a 20 AWG Cross section of 1020 circular mils, 17 AWG will be approximately 2040 mils and 23 AWG will be approximately 510 circular mils.

Using this relationship, with the commitment to memory of the cross-sectional area, resistance and mass per unit for any one size, you can quickly move to the value for any other wire size.

For diameter calculation, remembering one diameter, the diameter will double or halve every size gauges and for each gauge the next larger gauge diameter is 120% or 1.2 times the smaller gauge. If you remember six contiguous gauges in mils e.g. 39 - 44 AWG, you would know all diameters by this rule. Actually, if you just remember 39 AWG as 3.5 mils and the spread between these gauges is 0.3 mil except between 39 and 40 where it is 0.4 mil and 23 and 44 is 0.2 mil, you will have quick access to all gauge diameters.

* Information to be used as guide only. *