WireGaugeCalc Free calculator · NEC cited · works offline
Right Wire Size
Right wire size is fast with WireGaugeCalc, since you enter the load amps, conductor material, and termination temperature.
It checks the load against NEC 310.16 ampacity, so it returns a copper or aluminum size that carries the current.
You get an AWG or kcmil result with the matching ampacity, so you can pull the correct conductor the first time.
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.
How NEC 310.16 Sizing Works
Each conductor size has a rated ampacity in NEC Table 310.16 that depends on insulation rating and material.
Since terminations are rated 60, 75, or 90 degrees C, the calculator reads ampacity from the column that matches your equipment.
It compares your load to that ampacity, so the result is a size with enough capacity.
What the Conductor Sizing Tool Checks
Give the tool your load details and it returns the size:
- Copper versus aluminum ampacity from NEC 310.16
- Termination temperature column at 60, 75, or 90 degrees C
- Continuous loads sized at 125 percent
- AWG and kcmil result with rated ampacity
- Voltage-drop note for long runs
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
Which temperature column should I size from?
Use the column that matches the lowest-rated termination on the circuit, often 75 degrees C for breakers and lugs. Verify the ratings on your specific equipment and the current NEC with your local authority having jurisdiction.
Why is the right wire size different for aluminum?
Aluminum has lower ampacity than copper at the same gauge, so it usually needs a larger size to carry the same load. The calculator applies the correct ampacity for the material you pick.
Does the result account for voltage drop?
Ampacity comes first, but long runs can still drop too much voltage. The tool flags long runs so you can upsize if the drop exceeds the 3 percent branch-circuit guideline.
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.