WireGaugeCalc Free calculator · NEC cited · works offline
Service Panel Wire Size Calculator
Service panel wire size calculator results are quick with WireGaugeCalc, since the tool runs on this page.
You enter the panel amp rating, pick copper or aluminum, and choose the termination temperature column for the lugs.
That means you get the conductor size for the panel without hand-reading the NEC ampacity 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.
Sizing service conductors to the panel rating
A panel needs conductors rated for its full amp rating, so a 200A panel calls for conductors that carry 200A.
WireGaugeCalc uses NEC 310.16 and the column you pick to return the matching AWG or kcmil.
Since lug ratings vary, you set the termination temperature and the result follows that limit.
Copper vs aluminum feeder choices
The calculator works from a short list of inputs:
- Panel amp rating, such as 100A or 200A
- Copper or aluminum conductor
- 60C or 75C termination column
- Service entrance or feeder conductor
- Result in AWG or kcmil
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 the dwelling service table instead of 310.16?
NEC 310.12 allows smaller conductors for many single-dwelling services and feeders. The calculator focuses on standard ampacity, so confirm whether the dwelling allowance applies and verify against the current NEC and your local authority having jurisdiction.
What aluminum size is common for a 200A residential panel?
4/0 aluminum is common for a 200A dwelling service under the dwelling table, while standard ampacity calls for a larger size. Enter your conditions to see the exact result for your install.
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.