WireGaugeCalc Free calculator · NEC cited · works offline
Sizing Conductor Ampacity
sizing conductor ampacity is simple with WireGaugeCalc, since you enter the gauge, material, and conditions and the tool returns the rated amps.
The calculator reads the correct NEC 310.16 temperature column and applies any derating for heat and conductor count.
You see whether the conductor safely carries your load before you commit to it.
Open the calculatorAllowable ampacity from NEC Table 310.16 at the chosen termination temperature. Field aid only, verify against the current NEC and your local authority having jurisdiction.
Termination Temperature Columns Set The Limit
Ampacity comes from the column that matches the equipment terminations, so most circuits are read at the 75C column.
A 90C conductor can use the higher column only for derating math, so the final value still bows to the 75C termination.
Because heat and bundling reduce capacity, the tool applies ambient and conduit-fill adjustment factors to the base ampacity.
Inputs For Conductor Ampacity
Tell the calculator about the conductor and its conditions:
- Conductor gauge and material
- Insulation temperature rating, 60C, 75C, or 90C
- Termination temperature of the equipment
- Ambient temperature for correction
- Number of current-carrying conductors
- Result as the adjusted ampacity in amps
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 90C column to carry more current?
Only for the derating calculation. The final ampacity is limited to the termination temperature, usually 75C, so the 90C value cannot exceed what the lugs are rated for.
How many conductors trigger ampacity derating?
More than three current-carrying conductors in a raceway require an adjustment factor per the NEC. Confirm the count, the factor, and the temperature column 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.