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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.

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ptss

Showing 1 response by gs5556

gs5556
1,209 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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