WireGaugeCalc Free calculator · NEC cited · works offline
Dc Current Wire Size Calculator
Dc current wire size calculator is simple with WireGaugeCalc, since it sizes a conductor from DC amps, one-way run length, and voltage drop.
You enter the load current, the distance, and the system voltage, so the tool weighs ampacity and drop together.
The result is a gauge that carries the load and keeps voltage within your target along the whole run.
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.
How A 12 Volt Wire Gauge Calculator Works
DC runs often fail on voltage drop before ampacity, since long low-voltage runs lose a large share of the supply.
A 12 volt wire gauge calculator weighs both limits, so it returns the larger conductor that satisfies the tighter rule.
The tool checks NEC 310.16 ampacity at your termination temperature, so the gauge is safe for continuous load.
Inputs That Set Your DC Conductor Size
These details drive the gauge the tool returns:
- Load current in amps, the base for ampacity
- One-way run length, since DC drop scales with round-trip distance
- System voltage, because 12V tolerates less drop than higher voltage
- Allowable voltage drop, often 3 percent for a branch circuit
- Conductor material, copper or aluminum, which changes resistance
- Termination temperature column from NEC 310.16
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 a 12V run need bigger wire than a 24V run?
At 12V the same percentage drop allows fewer volts lost, so you need lower resistance and a larger conductor. Doubling the voltage roughly cuts the current and eases the drop for the same power.
Is voltage drop or ampacity the deciding factor?
On short runs ampacity usually controls, while on long runs voltage drop controls. The calculator sizes for whichever rule demands the larger conductor.
What voltage drop target should I use for DC?
A common guideline is 3 percent on a branch circuit, though sensitive loads may need tighter limits. Confirm the target and conductor sizing 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.