WireGaugeCalc Free calculator · NEC cited · works offline
15amp Circuit Wire Size
15amp circuit wire size is quick with WireGaugeCalc, since you enter 15 amps, the voltage, and the run length and the tool returns a conductor gauge.
The calculator pulls the NEC 310.16 ampacity for your conductor material and termination temperature, then it checks voltage drop on the run.
You get the right gauge for a 15 amp branch circuit before you reach for the wire spool.
Open the calculatorSmallest conductor whose ampacity meets the load, NEC Table 310.16. Field aid only, verify against the current NEC and your local authority having jurisdiction.
The Common Gauge For A 15 Amp Branch Circuit
A 15 amp circuit usually uses 14 AWG copper, since that gauge carries 15 amps at the 60 degree C column in NEC 310.16.
Aluminum needs a larger gauge for the same load, so the calculator adjusts when you switch material.
A long run can push the size up, since voltage drop grows with distance.
What Sets The 15 Amp Wire Size
The calculator weighs the factors that decide the gauge:
- NEC 310.16 ampacity at the 60 degree C column
- 14 AWG copper as the typical baseline
- Copper or aluminum conductor choice
- Termination temperature rating on the device
- Voltage drop checked against the 3% branch target
One app for every NEC calculation
WireGaugeCalc keeps the calculations you reach for most in one place:
- Voltage drop and wire sizing for any run
- Conduit fill for EMT, PVC, and RMC
- Box fill and junction box sizing
- Ampacity and temperature derating
- Motor circuit and load calculations
- Conduit bend offsets and saddles
Built for the field, works offline
The whole app runs on your phone, so it keeps working in a basement, an attic, or a job site with no signal.
There is no account to create and nothing to load. Open it, run the number, and get back to work.
- No signup and no signal needed
- Answers in a tap, not a spreadsheet
- Same tool on phone, tablet, and desktop
Every result cites the NEC article
Each answer shows the table or formula it came from, so you can check the method and learn the code as you go.
That makes the app useful on the job and during exam prep, since the reasoning is right next to the number.
Switch the code year your job runs on
Jurisdictions adopt the NEC at different times, so you can match the calculation to the code in force:
- NEC 2017, 2020, and 2023 tables
- Copper and aluminum conductors
- 60, 75, and 90 degree C terminations
- Single-phase and three-phase systems
Run the number, then get back to work
Stop flipping through a paper book or hopping between calculator sites. Enter your values, read the code-cited answer, and move on. Free to use, no signup.
Open the calculatorFrequently asked questions
Can I use 14 AWG on a 15 amp circuit?
Yes, 14 AWG copper is rated for 15 amps at the 60 degree C column in NEC 310.16, which matches a 15 amp breaker. Verify the breaker, conductor, and any derating against the current NEC and your local authority having jurisdiction.
When does a 15 amp circuit need a larger wire?
A long run can require upsizing, since voltage drop on the circuit can pass the 3 percent guideline. The calculator flags that and suggests a bigger gauge when distance is the limiting factor.
Is WireGaugeCalc free to use?
Yes. Every calculator is free to run with no signup. A paid tier adds saved projects, PDF reports, and extra code years, but the core math stays free.
Does it work without internet?
Yes. The app runs on your device, so it keeps working with no signal on a job site, in a basement, or in an attic.
Are the results code accurate?
Results follow published NEC tables and standard formulas, and each answer shows the article it came from. It is a field aid, not a stamp of approval, so verify against the current code and your local authority before you wire anything.
Which NEC code year does it use?
You can switch between NEC 2017, 2020, and 2023, since jurisdictions adopt the code at different times. Pick the year your job runs on.