WireGaugeCalc Free calculator · NEC cited · works offline
Distance Wire Size
Distance wire size is fast with WireGaugeCalc, since you enter the one-way run length, voltage, and load and the tool returns a conductor that fits.
It checks NEC 310.16 ampacity against your termination temperature and then confirms the gauge holds voltage drop within the usual 3% branch-circuit target over that distance.
So a long run gets sized once, and you avoid undersizing copper or aluminum on the way out.
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 Run Length Changes the Gauge
As distance grows, voltage drop rises, so a wire that passes ampacity at the panel can still fall short at the far end.
The calculator compares the ampacity-only size to the size needed for the run, then keeps the larger one so the load still gets full voltage.
It honors your conductor material, since aluminum carries less current per gauge than copper and needs an upsize on longer pulls.
What Goes Into Sizing for the Distance
Enter a few job details and the tool sizes the conductor for both heat and length:
- One-way run length in feet
- Load in amps and the system voltage
- Copper or aluminum conductor
- Termination temperature column, 60C, 75C, or 90C
- Single-phase or three-phase
- Target voltage drop, defaulted to 3%
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
How far can I run a circuit before I need to upsize the wire?
It depends on the load and voltage, but voltage drop near 3% is the common trigger to go up a gauge. The calculator flags the distance where your chosen size crosses that line. Verify the result against the current NEC and your local authority having jurisdiction.
Does the same distance need a bigger wire in aluminum than copper?
Yes, since aluminum has higher resistance per gauge, so it drops more voltage over the same run and usually steps up one or two sizes.
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.