Between its neighbours
18 AWG has 59 % more copper than 20 AWG and 37 % less than 16 AWG. Its DC resistance is 7.95 Ω per 1000 ft at 75 °C (aluminum 13.1), and 1000 ft of it carries 4.90 lb of copper.
18 AWG wire: amps, diameter & uses
18 AWG wire is 0.0403" (1.02 mm) solid and 0.82 mm². It is too small for house wiring (NEC minimum 14 AWG), but as flexible cord it is rated 10 A with two current-carrying conductors; at 12 V and 5 A it reaches 4 ft at 3 % drop. Used for lamp cords, thermostat and doorbell wire, 12 V accessories.
01 · 1:1 wire gauge · caliper
18 AWG · bare solid copper
THIS IS:
18 AWG COPPER · NOT BUILDING WIRE · 1.02 MM COPPER
Gauge
18 AWG
bare solid copper
Breaker
n/a
not building wire
Measured
1.02 mm
0.0403"
The gap is 1.02 mm (0.0403"), which reads as 18 AWG bare solid copper. Measure bare copper for the gauge: insulation is far thicker than the metal.
- Meets NEC 2023 Table 310.16 at 75°C — verify with your local AHJ/inspector310.16
- Drawn at true sizecalibrated screen
18 AWG
- Solid diameter
- 0.0403"1.024 mm · ASTM B258 formula
- Stranded (7 strands)
- 0.0460"1.168 mm · Table 8
- Area
- 1,620 cmil0.821 mm² · nearest IEC 0.75 mm²
- DC resistance, 75 °C
- 7.95 Ω/1000 ftaluminum 13.1 Ω/1000 ft · Table 8
- Copper weight
- 4.90 lb/1000 ft
Ampacity
- Copper 60 / 75 / 90 °C
- — / — / 14 ANM-B uses the 60 °C column (334.80)
- Aluminum 60 / 75 / 90 °C
- —
- Largest breaker (Cu, 75 °C)
- —ampacity ≥ breaker
Other gauges
- Nearest SWG
- SWG 190.04" · 1.016 mm
- IEC 60228
- 0.75 mm²between 0.75 and 1 mm²
18 AWG at a glance
Size
- Solid diameter
- 0.0403" · 1.02 mm
- Stranded (7)
- 0.046"
- Area
- 1,620 cmil · 0.821 mm²
- Metric
- 0.75 – 1 mm²
- SWG nearest
- 19 (1.016 mm)
Amps
- Copper 60/75/90 °C
- — / — / 14 A
- Aluminum 75 °C
- —
- Max breaker, THHN
- —
- As NM-B cable
- not made
- Ground for it
- —
Run & fit
- 120 V at 5 A
- 45 ft at 3 %
- 240 V at 5 A
- 90 ft at 3 %
- THHN in ½" EMT
- null
- THHN in ¾" EMT
- null
- Copper weight
- 4.9 lb/1000 ft
18 AWG reference 18 rows
Sort any column, print a shop sheet, download CSV. Click a row to load it in the calculator.
| Actions | ||||
|---|---|---|---|---|
| 22 | 226 | 452 | ||
| 11 | 113 | 226 | ||
| 4 | 45 | 90 | ||
| 2 | 22 | 45 |
| Actions | |||||||
|---|---|---|---|---|---|---|---|
| 0 | 0 | 0 | 0 | 0 | 0 | ||
| 0 | 0 | 0 | 0 | 0 | 0 | ||
| 0 | 0 | 0 | 0 | 0 | 0 | ||
| 0 | 0 | 0 | 0 | 0 | 0 | ||
| 0 | 0 | 0 | 0 | 0 | 0 | ||
| 0 | 0 | 0 | 0 | 0 | 0 | ||
| 0 | 0 | 0 | 0 | 0 | 0 |
05 / Field guide
18 AWG
cords and low voltage.
18 AWG wire is 0.0403" (1.02 mm) solid and 0.82 mm². It is too small for house wiring (NEC minimum 14 AWG), but as flexible cord it is rated 10 A with two current-carrying conductors; at 12 V and 5 A it reaches 4 ft at 3 % drop. Used for lamp cords, thermostat and doorbell wire, 12 V accessories.
Feeders and services
18 AWG is the usual choice for lamp cords, thermostat and doorbell wire, 12 V accessories. It is not made as NM-B cable; use THHN or XHHW in conduit, or SER/USE cable. The equipment ground for its largest breaker is null.
On the 1:1 gauge
The caliper above opens at 1.02 mm. Lay a stripped length along the lines and step the gauge with ← and → until the wire just fills the gap.
Questions
Answered plainly.
01How many amps can 18 AWG wire carry?
+−
18 AWG copper is rated — A at 60 °C, null A at 75 °C and 14 A at 90 °C (NEC Table 310.16, 30 °C, three conductors or fewer). Aluminum of the same size: — A at 75 °C.
02What size breaker for 18 AWG wire?
+−
Up to null A with THHN on 75 °C terminals.
03What is the diameter of 18 AWG wire?
+−
0.0403 inch (1.02 mm) solid, 0.046 inch stranded (7 strands).
04What is 18 AWG in mm²?
+−
0.821 mm² (1,620 circular mils). The IEC sizes either side are 0.75 and 1 mm²; replace it with 1 mm², not the smaller one.
05How far can 18 AWG wire run?
+−
At 5 A and 3 % drop, 45 ft one way at 120 V and 90 ft at 240 V (Table 8 resistance, 7.95 Ω per 1000 ft at 75 °C). Lighter loads go proportionally further.
06How far can 18 AWG speaker wire run?
+−
About 31 ft to an 8 Ω speaker and 15 ft to a 4 Ω one before the cable passes 5 % of the impedance (about 0.42 dB).
07What is 18 AWG in SWG?
+−
The nearest British Standard Wire Gauge is SWG 19 at 1.016 mm, against 1.02 mm for 18 AWG.