WireGaugeCalc Free calculator · NEC cited · works offline
#8 Aluminum Wire Ampacity
#8 aluminum wire ampacity is quick with WireGaugeCalc, since you pick the temperature rating and the app reads the right NEC 310.16 column.
The app returns the listed ampacity for 8 AWG aluminum at the 60, 75, or 90 degree C column.
So you can size protection and terminations from the same number.
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 the aluminum ampacity column
8 AWG aluminum is rated 30 amps at 60 degrees C, 40 amps at 75 degrees C, and 45 amps at 90 degrees C in NEC 310.16.
You apply the column that matches the lowest rated termination on the circuit, since the connection point limits the conductor.
Aluminum carries less current than copper of the same size because it has higher resistance.
What sets the usable ampacity
Several factors decide which number you can actually use:
- Termination temperature rating on the breaker and lugs
- Conductor insulation type such as XHHW or THHN
- Ambient temperature correction factors
- Number of current-carrying conductors bundled together
- Aluminum versus copper resistance
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 90 degree column for #8 aluminum on a breaker?
Usually no for the final rating. Most equipment terminations are listed at 75 degrees C, so you size to that column even when the insulation is rated 90 degrees C.
What is the ampacity of #8 aluminum at 75 degrees C?
8 AWG aluminum is 40 amps in the 75 degree C column of NEC 310.16 before any correction. Confirm corrections and terminations 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.