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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
 
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.


kijanki's avatar
kijanki
4,428 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).
#3 diameter is 0.2294" while #6 is 0.1620"
Wire diameter doubles for each 6 AWG decrease. 

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