WireGaugeCalc Free calculator · NEC cited · works offline
Electric Service Line Size
electric service line size is fast with WireGaugeCalc, since you enter the service rating and the tool reads the NEC ampacity tables.
It checks copper or aluminum at the 75 degree C termination column, so the conductors match the lugs in the panel and meter.
You get the AWG or kcmil size for the service entrance, so you can order the right feeder.
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.
Matching Conductors to the Service Rating
The calculator sizes the conductor so its ampacity meets or exceeds the service rating you enter.
It uses the 75 degree C column, since service equipment lugs are commonly rated for 75 degree C terminations.
Choose aluminum and the result moves to a larger size, as aluminum carries less current per gauge than copper.
What Sets the Service Conductor Size
The result depends on these inputs:
- Service rating in amps, such as 100, 150, or 200
- Conductor material, copper or aluminum
- Termination temperature column at the equipment
- Length of the run for any voltage drop check
- Whether the dwelling service optional table applies
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 a 200 amp service use smaller conductors than the standard table?
A dwelling service can sometimes use the optional sizing allowance in the NEC, which permits a reduced conductor for the main feeder. Confirm the exact application against the current NEC and your local authority having jurisdiction before you order wire.
Why does aluminum need a larger size for the same service?
Aluminum has lower ampacity per gauge than copper, so a higher kcmil or AWG is required to carry the same amps. The calculator steps the size up when you select aluminum.
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.