12 AWG wire is one of the most commonly used wire sizes in electric engineering. With 25A ampacity at a median of 75°C temperature, it is the best wire to be used for 20 amp services (of course, you have to account for 80% NEC requirement, as we explain later on).
We are going to systematically cover the basic features of a 12 AWG copper wire and contrast this wire to:
- Smaller 14 AWG wire (12 vs 14 AWG wire comparison).
- Bigger 12 AWG wire (12 vs 10 AWG wire comparison).
We are going to look into 12 AWG wire:
- Diameter (mm). Ie. 12 gauge wire in mm.
- Area or crosssection (mm2). Ie. 12 AWG to mm2.
- Number of turns of the wire per inch and per cm.
- Resistance of 12 AWG per meter and per foot (Ohms).
- Maximum current density per mm2.
- 12 AWG wire amp rating: ampacity at 60°C, 75°C, and 90°C.
- 12 AWG wire wattage. Ie. How much power can 12 AWG wire conduct?
Let’s start with the diameter:
12 AWG Wire Diameter (12 Gauge Wire In mm)
The diameter or thickness of any wire depends on the number and the cross-section of the individual wires that constitute the whole wire. In the case of 12 AWG wire diameter, we are going to look at a solid wire (stranded wires – with plastic insulation – are thicker).
12 gauge wire is 2.053 mm thick. This is equal to 0.0808 inches. Because the diameter of 12 AWG wire is so close to 2 milimeter we also refer to it as a ‘2 mm wire’.
If you compare the diameter of 12 AWG wire vs diameter of 14 AWG wire, you can see that 14 AWG has a 1.628 mm diameter. That means that the diameter of 14 AWG wire is about 21% smaller than the diameter of 12 AWG wire.
Compared to the bigger 10 AWG wire with a 2.588 mm diameter, the 12 AWG wire’s diameter is 26% smaller.
Cross-Section: 12 AWG To mm2
12 gauge wire area or cross-section also depends on the number and cross-section of the individual wires.
If you were to express the cross-section of 12 AWG to mm2, you can see that 12 AWG has an area of 3.31 mm2. These are squared millimeters; a unit for the surface.
In the US, kcmil units are also used for circular shapes. kcmil stands for kilo-circular mils. 1 kcmil is equal to about half of mm2 (0.5067 mm2, to be exact). A 12 gauge wire has an area of 6.53 kcmil.
Let’s compare the cross-section of 12 vs 14 AWG wires and 12 vs 10 AWG wires:
Compared to the smaller 14 AWG wire with a 2.08 mm2 cross-section, the 12 AWG wire is 37% bigger than the 14 AWG wire in area.
Compared to the bigger 10 AWH wire with a 5.26 mm2 cross-section, the 12 AWG wire is 59% smaller than the 10 AWG wire in area.
12 AWG Number Of Wire Turns
All AWG wires are made out of smaller individual wires. These small wires are spiral throughout the wire or cable. For some applications, it’s useful to know how many spirals there are in a 12 AWG wire.
12 gauge wire has 12.4 turns of wire per inch, and 4.87 turns of wire per cm (centimeter).
12 AWG Wire Resistance (Ohms)
With every wire, you have to take the resistance into account. Electrical resistance is measured in Ohms (Ω).
Resistance of 12 AWG copper wire is 5.211 milliohms per meter (mΩ/m). This translates to 1.588 milliohms per foot (mΩ/ft).
As far as resistance is concerned, copper wires are about 40% more efficient for transporting electricity than aluminum wires.
That’s why same-size copper wires carry more amps than aluminum wires. On top of that, with less resistance, the 12 AWG copper wires is more resistant to heat generation than a 12 AWG aluminum wire.
Current Density Of 12 Gauge Wire
Current density is a measure of how much electric current can a wire carry per mm2 of the cross-section. Current density is usually measured at 4A/mm2 current.
The maximum current density a 12 AWG wire can achieve is 13.2 amps per mm2 (13.2 A/mm2).
12 AWG Amps: Amp Rating Or Ampacity
How many amps can a 12 AWG wire handle? This is usually one of the most important specifications for any wire.
12 gauge wire can carry:
- 20 amps at 60°C (20A ampacity or amperage).
- 25 amps at 75°C (25A ampacity or amperage).
- 30 amps at 90°C (30A ampacity or amperage).
When sizing a wire, we usually take the median 75°C ampacity. That means that the ampacity of the 12 AWG wire is 25A.
Does that mean that 12 gauge wire can handle 25 amps?
Yes and no.
12 AWG wire can handle 25 amps of current but we use this wire as a 20 amp wire (more about this here). This is because we have to account for the 80% National Electric Code (NEC) requirement.
This requirement states that any wire used in circuits should carry at most 80% of the total amperage. In the case of 25A 12 AWG wire, this calculates to a 20 amp circuit.
That’s why 12 gauge wire is used as a 20 amp wire size.
12 AWG vs 14 AWG vs 10 AWG Amp Rating
Let’s compare the median amperage of the 12 AWG wire vs smaller 14 AWG wire and bigger 10 AWG wire. Here are the median ampacity ratings for all of these wires:
- 10 AWG wire has 35A ampacity (accounting for 80% NEC requirement, this is a 28 amp wire size).
- 12 AWG wire has 25A ampacity (accounting for 80% NEC requirement, this is a 20 amp wire size).
- 14 AWG wire has 20A ampacity (accounting for 80% NEC requirement, this is a 16 amp wire size).
As you can see from this list, the 12 AWG wire has 29% less ampacity than 10 AWG wire. If you check the amp rating for 12 vs 14 AWG wire, the 12 AWG wire has 25% more ampacity than the 14 AWG wire.
Overall, we hope that now you have a better understanding of the 14 AWG wire specifications. You can check the whole AWG wire chart with mm, mm2, and median ampacities here.
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