WireGaugeCalc Free calculator · NEC cited · works offline
105C Wire Ampacity
105C wire ampacity is fast with WireGaugeCalc, since you enter the conductor and the tool reads the high-temperature value and the usable one.
It shows the elevated insulation rating but then applies the termination temperature, since equipment lugs are commonly rated only 60C or 75C.
So you size to what the connection allows, not just what the insulation can take.
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.
High Insulation Rating Versus the Termination Column
A 105C insulation rating helps with ambient heat and derating, but it rarely raises the final ampacity by itself.
Since the NEC sets ampacity at the lowest-rated component, a 75C lug caps the conductor at its 75C value.
The calculator shows both numbers, so you can use the 105C column for derating math while sizing to the termination.
Inputs the Calculator Uses
Give the tool the conductor details and it returns the ampacity that governs:
- Conductor size and material
- Insulation rating, including 105C
- Termination temperature, 60C or 75C
- Ambient temperature for derating
- Number of current-carrying conductors
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 full 105C ampacity to size a circuit?
Usually not for the final size, since the termination temperature limits the result, often to the 75C value. The higher column is mainly for ambient and bundling derate calculations. Confirm against the current NEC and your local authority having jurisdiction.
Where does 105C insulation help if the terminals are only 75C?
It gives you more headroom when derating for high ambient or many conductors, so the corrected ampacity stays above the load even though the termination still sets the cap.
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.