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Guide for understanding wire gauge and resistance

The AWG is a logarithmic scale, so given an know resistance or diameter for a certain gauge, you can quickly figure out the resistance and diameter of another gauge number, by addition and subtraction.

Resistance:

  1. AWG 15 is 10 mohm/m.
  2. Adding 3 doubles the resistance, and subtracting 3 halves it.
  3. Adding 10 multiplies the resistance by 10, and subtracting 10 it divides by 10.

Diameter:

  1. AWG 18 has a solid diameter of about 1mm
  2. Adding 6 halves the diameter, Subtracting 6 doubles the diameter
  3. Adding 20 divides the diameter by 10, and subtracting 20 multiplies the diameter by 10.

 I picked this up from the DAYCOUNTER, INC Engineering Services website. They provide an array of services and technical information.

ptss
kijanki's avatar
kijanki
4,428 posts
 
Read carefully again - RESISTANCE.  As for impedance - it usually doesn't drop below couple of ohms making 10 miliohms irrelevant.
mgattmch
573 posts
 
Thanks PTSS, being a European AWG makes little sense to me. Now I can easily convert to units that I understand.
kijanki's avatar
kijanki
4,428 posts
 
People usually think of speaker gauge when they calculate Damping Factor forgetting that speaker/driver resistance is in series with back EMF making best effective DF around 1.25
testpilot
952 posts
 
ptss, please explain to me how AWG is a logarithmic scale???
gs5556
1,236 posts
 
Just another take on the rule of thumb that wire diameter doubles for each 3 AWG unit decrease (i.e., #3 is twice the diameter of #6).

Adding three doubles the resistance since the area is halved and resistance is proportional to the inverse of the cross-sectional area per unit length.


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