WireGaugeCalc Free calculator · NEC cited · works offline
Dc Motor Wire Size Calculator
dc motor wire size calculator is simple with WireGaugeCalc, since you enter the motor full-load current and the tool returns the conductor from NEC 310.16.
It accounts for conductor material and termination temperature, so the gauge matches the lugs and the overcurrent device.
The payoff is a conductor sized for the motor before you cut a single foot of cable.
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.
Sizing The DC Motor Branch Circuit
A motor circuit is sized at 125 percent of the full-load current, so the calculator bumps the rating before reading the NEC 310.16 ampacity.
Switching between copper and aluminum changes the conductor instantly, since each material hits the required ampacity at a different size.
Long DC runs can drop voltage, so the tool flags when a larger conductor protects the motor torque.
What The Motor Wire Calculation Uses
The conductor for a DC motor depends on:
- Motor full-load current in amps
- The 125 percent continuous-duty factor for motor circuits
- Conductor material, copper or aluminum
- Termination temperature column, usually 75C
- Run length, since DC voltage drop affects torque
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
Do I size DC motor wire at 125 percent of full-load current?
Yes, NEC motor rules size the branch-circuit conductor at 125 percent of the motor full-load current. The calculator applies that factor before reading ampacity. Confirm the value against the current NEC and your local authority having jurisdiction.
Does voltage drop matter more on DC motor circuits?
Often yes, since DC runs at lower voltages lose torque as voltage drops over distance. For long runs, size up the conductor to keep voltage drop near 3 percent at the motor.
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.