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AWG Wire Sizes (see table on the next page)
AWG: In the American Wire Gauge (AWG), diameters can be calculated by applying the formula
D(AWG)=.005·92((36‑AWG)/39) inch. For the 00, 000, 0000 etc. gauges you use ‑1, ‑2, ‑3, which makes
more sense mathematically than “double nought.” This means that in American wire gage every 6 gauge
decrease gives a doubling of the wire diameter, and every 3 gauge decrease doubles the wire cross sectional
area. Similar to dB in signal and power levels. An approximate form of this formula contributed by Mario
Rodriguez is D = .460 * (57/64)(awg +3) or D = .460 * (0.890625)(awg +3).
Metric Wire Gauges (see table on the next page)
Metric Gauge: In the Metric Gauge scale, the gauge is 10 times the diameter in millimeters, so a 50 gauge
metric wire would be 5 mm in diameter. Note that in AWG the diameter goes up as the gauge goes down, but
for metric gauges it is the opposite. Probably because of this confusion, most of the time metric sized wire is
specied in millimeters rather than metric gauges.
Load Carrying Capacities (see table on the next page)
The following chart is a guideline of ampacity or copper wire current carrying capacity following the Handbook
of Electronic Tables and Formulas for American Wire Gauge. As you might guess, the rated ampacities are
just a rule of thumb. In careful engineering the voltage drop, insulation temperature limit, thickness, thermal
conductivity, and air convection and temperature should all be taken into account. The Maximum Amps for
Power Transmission uses the 700 circular mils per amp rule, which is very conservative. The Maximum
Amps for Chassis Wiring is also a conservative rating, but is meant for wiring in air, and not in a bundle. For
short lengths of wire, such as is used in battery packs you should trade off the resistance and load with size,
weight, and exibility. NOTE: For installations that need to conform to the National Electrical Code, you must
use their guidelines. Contact your local electrician to nd out what is legal!
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