WireGaugeCalc Free calculator · NEC cited · works offline
Dc Wire Size Calculator
dc wire size calculator is fast with WireGaugeCalc, since you enter the system voltage, the load in amps, and the one-way run length and it returns a conductor gauge.
The tool checks the result against NEC 310.16 ampacity for the conductor material and termination temperature you pick, so the gauge carries the load and stays inside the voltage drop you allow.
You get a defensible DC wire size in seconds, so you can spec the run before you cut and crimp.
Open the calculatorSmallest conductor whose ampacity meets the load, NEC Table 310.16. Field aid only, verify against the current NEC and your local authority having jurisdiction.
Why a 12v wire size calculator depends on run length
Low DC voltage leaves little headroom, so a long run drops a large share of the supply before it reaches the load.
A 12v wire size calculator weighs current against distance, since doubling the round-trip length doubles the resistance and the drop.
WireGaugeCalc upsizes the conductor when the drop crosses your limit, so the device at the end still sees usable voltage.
What a 12 volt wire size calculator needs from you
Give the tool four inputs and it sizes the conductor:
- System voltage, such as 12V or 24V DC
- Continuous load current in amps
- One-way run length in feet
- Conductor material, copper or aluminum
- Allowable voltage drop, often 3 percent
- Termination temperature column, 60, 75, or 90 degrees C
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
Why does my 12V run need such a heavy wire?
At 12V a small percentage drop is only a fraction of a volt, so even modest current over a long run forces a larger gauge to hold the voltage. Shortening the run or raising the system voltage both let you use smaller wire.
Do I size DC wire on ampacity or voltage drop?
Size for both and use the larger result. Ampacity from NEC 310.16 keeps the conductor from overheating, while voltage drop keeps the load working, and DC runs are usually driven by voltage drop. Confirm the final size 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.