WireGaugeCalc Free calculator · NEC cited · works offline
Number 2 Thhn Ampacity
Number 2 thhn ampacity is quick to confirm with WireGaugeCalc, since the app reads NEC Table 310.16 and returns the rated value for the conductor.
You pick copper or aluminum and the termination temperature, and the calculator returns the ampacity from the matching column.
The payoff is a number you can size a breaker against without flipping through the code book.
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.
Reading 2 AWG THHN From Table 310.16
THHN is a 90C insulation, so the conductor can be derated from the 90C column, but the final rating is held to the terminal it lands on.
Since most equipment is rated 75C, copper 2 AWG is read at 115 amps and aluminum at 90 amps in that column.
The 90C column is used for derating math, then the answer is checked against the lower termination rating.
What Sets the 2 AWG THHN Rating
These inputs decide the usable ampacity:
- Conductor material, since copper carries more than aluminum at the same size
- Termination temperature, which caps the value at 60C, 75C, or 90C
- Number of current-carrying conductors in the raceway, which triggers adjustment
- Ambient temperature, which can lower the rating in hot spaces
- Continuous load, where the breaker is sized at 125 percent
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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 for number 2 THHN to size my breaker?
No, the 90C rating is only for derating calculations. The final ampacity is limited to the termination temperature, which is usually 75C, so 2 AWG copper THHN is treated as 115 amps for terminal sizing.
What ampacity does 2 AWG aluminum THHN carry?
Aluminum 2 AWG sits at 90 amps in the 75C column of Table 310.16. Verify the value against the current NEC edition and your local authority having jurisdiction before final sizing.
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.