WireGaugeCalc Free calculator · NEC cited · works offline
Size Wire For House Feed
size wire for house feed is fast with WireGaugeCalc, which returns the conductor that carries your amperage.
It reads the NEC 310.16 ampacity table for copper or aluminum at the termination temperature, so the feeder matches the breaker.
You know the right gauge before ordering the wire.
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.
Match the house feeder to its load
A house feeder must carry the full load amperage, so the calculator starts from the service or subpanel rating.
Aluminum carries less current than copper of the same size, so the result sizes up on aluminum.
Termination temperature sets which 310.16 column applies, so the gauge lands where the lugs can accept it.
Inputs that size a house feeder
Give the calculator a few values and it returns the conductor:
- Service or subpanel amperage
- Copper or aluminum conductor
- Termination temperature rating
- Single-phase or three-phase supply
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 size wire do I need for a 200 amp house feed?
A common answer is 2/0 copper or 4/0 aluminum at the 75 degree column for a 200 amp feeder, but it depends on your terminations and any derating. Confirm the result against the current NEC and your local authority having jurisdiction.
Should I size to the 60 or 75 degree column?
Use the termination temperature marked on the breaker and lugs, since the lowest rated part sets the column. The tool lets you pick the column so the feeder matches your equipment.
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.