WireGaugeCalc Free calculator · NEC cited · works offline
Dc Wire Ampacity
dc wire ampacity is fast with WireGaugeCalc, since it reads conductor size and material and reports the rated current from the NEC ampacity columns.
You pick the wire size, copper or aluminum, and the temperature column, and the calculator shows the allowable current.
That value tells you whether a conductor can carry your DC load safely.
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.
How the termination temperature column sets the rating
Ampacity is limited by the lowest-rated termination, so the app lets you read the 60, 75, or 90 degree column that matches your terminals.
The 90 degree column is only for derating, since the usable dc wire size amperage is capped at the 60 or 75 degree value at the lugs.
Copper carries more current than aluminum at the same size, so the material you choose changes the result.
What sets the safe current on a DC run
Several factors decide the conductor you need:
- Conductor size in AWG or kcmil
- Copper versus aluminum material
- Termination temperature rating at both ends
- Ambient temperature and bundling derates
- Voltage drop on long DC runs, often tighter than AC
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
What wire size do I need for a 15 amp DC circuit?
For a 15 amp DC circuit wire size, 14 AWG copper carries 15 amps in the 60 degree column, but long DC runs often need a larger conductor for voltage drop. Verify the final size against the current NEC 310.16 and your local authority having jurisdiction.
Does NEC ampacity apply to DC circuits?
Yes, the NEC ampacity tables are based on conductor heating, which is the same for DC and AC at a given current. The main difference is that DC systems often run at lower voltage, so voltage drop, not ampacity, can set the wire size.
Which temperature column should I use?
Use the column that matches the lowest-rated termination on the circuit, which is usually 60 degrees for 14 to 10 AWG and 75 degrees for larger conductors with rated lugs.
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.