WireGaugeCalc Free calculator · NEC cited · works offline
Mv Voltage Drop Calculator
Mv voltage drop calculator is quick with WireGaugeCalc, since the app multiplies current, resistance, and run length to return the drop in volts and percent.
You enter the conductor size, one way distance, load current, and copper or aluminum, and the app does the math.
You get the percent drop in seconds, so you can compare it to the common 3 percent branch circuit guideline before pulling wire.
Open the calculatorUses Vd = (phase factor × K × I × L) / circular mils, K = 12.9 copper, 21.2 aluminum. Field aid only, verify against the current NEC and your local authority having jurisdiction.
How the percent voltage drop is calculated on a long run
Voltage drop rises with distance, so a longer one way run length increases the loss on the same conductor.
Larger conductors have less resistance, since more copper or aluminum cross section lowers the ohms per foot.
Copper drops less than aluminum at the same size, so material choice changes the result directly.
What the voltage drop result depends on
Four inputs set the drop on any run, so enter each carefully:
- Conductor size in AWG or kcmil
- One way run length in feet
- Load current in amps
- Copper or aluminum conductor material
- Single phase or three phase system
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 voltage drop percent is acceptable?
The NEC recommends about 3 percent on a branch circuit and 5 percent total for feeder plus branch. These are guidelines, so confirm any limit against the current NEC and your local authority having jurisdiction.
How do I cut voltage drop on a long run?
Increase the conductor size or shorten the run, since both lower the resistance the current sees. Switching from aluminum to copper at the same size also reduces the drop.
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.