WireGaugeCalc Free calculator · NEC cited · works offline
Amp Wire Size
amp wire size is quick with WireGaugeCalc, since you enter the current and the tool returns a conductor that carries it.
The calculator reads NEC 310.16 ampacity for copper or aluminum at your termination temperature, so the gauge matches the load instead of a rough guess.
You move from amps to a defensible conductor in one step, so the wire never runs past its rating.
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.
Going from awg to amps and back
Each gauge has a rated ampacity, so awg to amps is a direct lookup once you fix the material and temperature column.
Run it the other way and the same table turns a current into a gauge, since you simply pick the smallest conductor that meets the load.
WireGaugeCalc handles both directions, so you can check a gauge or size a new run from the same screen.
What amp to wire size depends on
The conductor for a given current shifts with a few inputs:
- Load current in amps
- Conductor material, copper or aluminum
- Termination temperature, 60, 75, or 90 degrees C
- Ambient temperature for derating
- Number of current-carrying conductors bundled together
- Run length when voltage drop matters
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
Does gauge to amps change with copper versus aluminum?
Yes. Aluminum carries less current than copper at the same gauge, so a gauge to amps lookup gives a lower rating for aluminum. Always set the material before reading the ampacity.
Which temperature column should I use for amp to wire size?
Use the lowest temperature rating among the wire, the breaker, and the device terminals, since the weakest link controls the rating. Many installs land in the 75 degree C column, but verify the terminations and the current NEC with your local authority having jurisdiction.
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.