WireGaugeCalc Free calculator · NEC cited · works offline
100 Amp Wire Gauge
100 amp wire gauge is quick with WireGaugeCalc, since the calculator reads NEC 310.16 ampacity for your conductor material and termination temperature.
You choose copper or aluminum and the rated terminal temperature, and the tool returns a gauge that carries 100 amps.
So you can size the feeder or service conductor without guessing at the table.
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.
Picking the Gauge from 310.16
Conductor material drives the size, since aluminum carries less current than copper and needs a larger gauge for 100 amps.
Termination temperature sets the column, so a 75C lug holds you to the 75C ampacity even if the insulation is rated for more.
What Sizes a 100 Amp Conductor
A few details decide the gauge you run:
- Conductor material, copper or aluminum
- Termination temperature rating, often 75C
- Ambient temperature and any derating
- Number of current-carrying conductors in the raceway
- Whether the run is a service or a feeder
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
What wire gauge do I need for a 100 amp service?
Sizing follows NEC 310.16 at the termination temperature, commonly 75C, and the answer differs for copper and aluminum. Enter your material and termination temperature and the calculator returns the gauge for 100 amps.
Is aluminum acceptable for a 100 amp feeder?
Yes, aluminum is allowed, but it needs a larger gauge than copper since its ampacity is lower at the same size. Confirm the result against the current NEC and 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.