# 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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8 responses
 01-16-2017 9:26pmPtss, I understand you posted this in the context of the speaker cable resistance.  Please take into consideration that most of the speaker impedance is resistive.  8 ohm speaker  will have, most likely, resistance of 6 ohm.  Your 10 mohms, in comparison, means nothing. 01-16-2017 11:28pm"8 ohm speaker will have, most likely, resistance of 6 ohm."TOTAL NONESENSE!The typical 8 ohm speaker has a "roller coaster", of varying, impedance (resistance, capacitance, inductance), across the audible audio frequency spectrum. 01-17-2017 4:28amRead carefully again - RESISTANCE.  As for impedance - it usually doesn't drop below couple of ohms making 10 miliohms irrelevant. 01-17-2017 4:59amThanks PTSS, being a European AWG makes little sense to me. Now I can easily convert to units that I understand. 01-17-2017 5:31amPeople 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 01-17-2017 6:30pmptss, please explain to me how AWG is a logarithmic scale??? 01-17-2017 10:18pmJust 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. 01-18-2017 4:25amJust 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.