What Is AWG? The Number That Sets Resistance
Quick answer / TL;DR: Short answer: AWG is a wire diameter scale where a larger number means a thinner conductor. Every three steps roughly halves the cross-sectional area and doubles the resistance. For Ethernet, 23 or 24 AWG is normal; for speaker runs, 16 or 14 AWG; for DC power at a few amps, 18 AWG or thicker.
Two measurements, one consequence: AWG sets the loss, OD sets the fit.AWG stands for American Wire Gauge, and it is the single number that most directly predicts how a cable will perform over distance. It runs backwards from intuition: 24 AWG is thinner than 18 AWG, and thinner means more resistance.
The count dates to wire drawing: each gauge step is a fixed ratio in diameter, so the number records how many passes through a die the metal took. That history is why the useful numbers sit in the middle of the scale rather than at zero.
How the Scale Actually Works
Each AWG step multiplies the diameter by about 0.89. Because resistance depends on cross-sectional area, not diameter, the practical rule is that three gauge steps roughly double the resistance. That is why 24 AWG is not a little worse than 22 AWG; it is meaningfully worse over a long run.
| AWG | Diameter (mm) | Resistance (ohm per 1000 ft) | Typical use |
|---|
| 12 | 2.05 | 1.6 | High-current DC, 70 V speaker lines |
| 14 | 1.63 | 2.5 | Speaker runs, long DC feeds |
| 16 | 1.29 | 4.0 | Speaker cable, short DC |
| 18 | 1.02 | 6.4 | Patch cables, low-current DC |
| 22 | 0.64 | 16.1 | Thin patch cable, alarm wiring |
| 23 | 0.57 | 20.4 | Cat6 Ethernet |
| 24 | 0.51 | 25.7 | Cat5e and slim Cat6 |
| 28 | 0.32 | 65.3 | Slim HDMI and USB pigtails |
What Changes When You Change Gauge
Three effects matter to a buyer. Resistance rises, which means voltage drop on power and attenuation on signal. Heat rises for the same current, because power loss is current squared times resistance. And stiffness rises as the wire thickens, which decides whether a cable can turn inside a small enclosure.
- Power: voltage drop equals current times loop resistance, so gauge sets usable length
- PoE: thinner conductors waste more of the 57 V budget as heat
- Speaker lines: gauge interacts with impedance; see the 5 percent rule
- Signal: attenuation rises with frequency, so long high-speed runs need thicker or active cable
The Gauges That Matter by Product
| Product | Common gauge | Why |
|---|
| Cat5e patch | 24 AWG | Flexibility in patch panels |
| Cat6 horizontal | 23 AWG | Lower attenuation for 250 MHz |
| Cat6A | 22 to 23 AWG | Shielding and higher frequency |
| Speaker cable | 16 to 12 AWG | Current and damping factor |
| Coax RG6 | 18 AWG centre | 75 ohm geometry, not current |
| USB charging cable | 20 to 28 AWG | Power pair thicker than data pair |
Note the last row. A USB cable often has two gauges inside: a thick pair for power and thin pairs for data. This is why a cable can charge quickly and still transfer data slowly, and why the outside diameter tells you almost nothing about the conductors.
Real-World Applications
Choosing speaker wire by run length
With a 5 percent loop-resistance rule against an 8 ohm load, 16 AWG supports roughly 50 ft, 14 AWG about 80 ft, and 12 AWG around 125 ft. Beyond that the amplifier loses damping control before the cable melts, so the symptom is loose bass rather than obvious failure.
Long PoE runs
At 30 W over 100 m, the difference between 23 and 24 AWG is a few watts of heat spread along the bundle. In a packed conduit that heat accumulates. Specifying 23 AWG or better for high-power PoE is a thermal decision as much as an electrical one.
Slim patch cables in a dense rack
28 AWG patch cords solve airflow and bend-radius problems in a full rack, but their resistance limits PoE. Use them for data-only links and keep higher-gauge cords for powered devices.
Standards and Verification
Conductor sizes and resistance values follow ASTM B258 for the gauge table and are restated in the TIA and IEC cable standards. The electrical limits referenced above come from those documents plus IEEE 802.3 for PoE.
- ASTM B258: standard nominal diameters for AWG
- TIA-568.2-D: balanced twisted-pair performance categories
- IEC 60228: conductor classes and resistance
- IEEE 802.3af, at, bt: PoE power and loss budgets
To verify a cable, measure conductor resistance with a four-wire method or check the printed gauge on the jacket against the actual conductor diameter with a micrometer. Copper-clad aluminium will pass a diameter check and fail a resistance check.
Related reading: Cat6 cable construction — blogs/news/cat6-cable
Related reading: 24 AWG Cat6 cable — blogs/news/24-awg-cat6-cable
Related reading: 22 AWG Ethernet cable — blogs/news/22-awg-ethernet-cable
Frequently Asked Questions
Is a higher AWG number thicker or thinner?
Thinner. AWG runs backwards from intuition: 24 AWG is thinner than 18 AWG, has more resistance per metre and carries less current.
What gauge is Cat6 cable?
Most Cat6 horizontal cable uses 23 AWG conductors. Cat5e typically uses 24 AWG, and Cat6A is usually 22 or 23 AWG because the higher frequency needs lower attenuation.
What AWG should speaker wire be?
16 AWG suits runs up to about 50 ft at 8 ohms, 14 AWG about 80 ft, and 12 AWG around 125 ft, using a 5 percent loop-resistance rule.
Does AWG affect PoE performance?
Yes. Thinner conductors have higher resistance, so more of the available power is lost as heat in the cable. For high-power PoE, specify 23 AWG or thicker.
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