WireGaugeCalc Free calculator · NEC cited · works offline
Low Voltage Wire Size Calculator
low voltage wire size calculator is quick with WireGaugeCalc.
You enter the system voltage, the load in amps, and the one-way run length, and the tool returns a conductor that holds the voltage drop in check.
So a 12V or 24V run reaches the load without starving it.
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 Voltage Drop Drives Low Voltage Sizing
At 12V or 24V a small drop is a large share of the supply, so run length and load set the conductor size more than ampacity does.
Since copper has lower resistance than aluminum, the tool holds your material choice while it sizes the run.
It targets a tight drop on the round-trip distance so the device sees enough voltage.
Inputs For A Low Voltage Run
The calculator sizes the conductor from:
- System voltage, such as 12V or 24V
- Load in amps
- One-way run length
- Conductor material, copper or aluminum
- Your acceptable voltage drop percentage
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 low voltage need bigger wire than I expect?
Voltage drop is the same volts whatever the supply, so at 12V it eats a large percentage and forces a larger conductor on long runs. The tool sizes for the round-trip distance to keep the drop low.
Does the NEC 3 percent guideline apply to low voltage?
The 3 percent branch-circuit figure is a common target, though low voltage devices often need tighter drop to work right. Confirm the limit for your equipment and check the current NEC with 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.