15 Amp Wire Size
What size wire for a 15 A load? The answer depends on terminations, continuous load and conductor material. Both 60 °C and 75 °C answers, under NEC 2026.
Updated
For reference only. Always verify with the NEC edition adopted by your AHJ.
Wire size for a 15 A load
The answer depends on the terminations. Under 110.14(C)(1), circuits of 100 A or less, and 14-1 AWG conductors, default to the 60 °C column of Table 310.16. Use the 75 °C answer only if all terminations are listed/marked for 75 °C. Both are for 90 °C insulation (such as THHN), 30 °C ambient and no more than 3 current-carrying conductors.
| Conductor | 60 °C terminations | 75 °C terminations |
|---|---|---|
| Copper | #14 AWGMax OCPD 15A (240.4(D)) | #14 AWGMax OCPD 15A (240.4(D)) |
| Aluminum | #12 AWGMax OCPD 15A (240.4(D)) | #12 AWGMax OCPD 15A (240.4(D)) |
If 15 A is a continuous load
A continuous load runs three hours or more. 210.19(A)(1) and 215.4(A)(1) size the conductor at 125%, so 15 A becomes 18.75 A. The overcurrent device is sized to the same 125%, so it will be larger than 15 A.
| Conductor | 60 °C terminations | 75 °C terminations |
|---|---|---|
| Copper | #12 AWGMax OCPD 20A (240.4(D)) | #12 AWGMax OCPD 20A (240.4(D)) |
| Aluminum | #10 AWGMax OCPD 25A (240.4(D)) | #10 AWGMax OCPD 25A (240.4(D)) |
What these answers leave out
- Small conductors have a breaker cap. Under 240.4(D), overcurrent protection is limited to 30 A for 10 AWG copper, 20 A for 12 AWG copper, 15 A for 14 AWG copper, 25 A for 10 AWG aluminum, 15 A for 12 AWG aluminum. Where it applies, the table shows it as Max OCPD.
- Ambient above 30 °C (310.15(B)(1)) and more than 3 current-carrying conductors (310.15(C)(1)) reduce ampacity and can raise the size. Use the calculator to include them.
- Voltage drop is not included; long runs may need a larger conductor.
15 amp wire size questions
- What size wire is needed for a 15 A load?
- It depends on the conductor and the terminations. For a 15 A noncontinuous load in copper (90 °C insulation, 30 °C ambient, 3 or fewer current-carrying conductors): #14 AWG when the terminations are limited to 60 °C, and #14 AWG only if all terminations are listed/marked for 75 °C (110.14(C)(1)). In aluminum: #12 AWG at 60 °C and #12 AWG at 75 °C. Voltage drop is not included; long runs may need a larger conductor.
- Does a continuous load change the wire size for 15 amps?
- Yes. A continuous load (3 hours or more) is sized at 125% under 210.19(A)(1) and 215.4(A)(1), so 15 A becomes 18.75 A. In copper that is #12 AWG at 60 °C and #12 AWG at 75 °C. The overcurrent device must be sized to the same 125%, so it is larger than 15 A.
- Does 240.4(D) limit a 15 A load?
- Yes for the smallest sizes. Under 240.4(D), conductors cannot be protected above 30 A for 10 AWG copper, 20 A for 12 AWG copper, 15 A for 14 AWG copper, 25 A for 10 AWG aluminum, 15 A for 12 AWG aluminum, so a 15 A load cannot use one that is capped lower.
- Why does the 15 A answer depend on 60 °C or 75 °C?
- 110.14(C) limits the ampacity to the lowest temperature rating of the conductor and its terminations. Circuits of 100 A or less, and 14-1 AWG conductors, default to the 60 °C column unless the equipment is marked for 75 °C, so the 60 °C answer is the safe default and the 75 °C answer needs every termination to be listed for it.
Other sizes
You can read the NEC 2026 for free at NFPA free access. Need another load? Use the wire size calculator.