WireGaugeCalc Free calculator · NEC cited · works offline
PV Wire Roof Conduit
pv wire roof conduit sizing is fast with WireGaugeCalc, since you enter the raceway type and each conductor and the tool returns the fill percentage.
It counts every PV conductor and ground, then compares the total area against the 40 percent limit from NEC Chapter 9 so you know the EMT or PVC is legal.
You leave with a clear pass or fail before you mount a single strut on the roof.
Open the calculatorFill against NEC Chapter 9, Table 1 (40% for 3+ conductors) with Table 4 and Table 5 areas. Field aid only, verify against the current NEC and your local authority having jurisdiction.
Why Roof Conduit Fill Matters for Solar Runs
Rooftop PV conductors run hot, so packing them tight in a small raceway traps heat and forces ampacity derating.
Staying at or under 40 percent fill keeps the conductors from binding during a pull and leaves room for heat to move.
WireGaugeCalc shows the live fill number as you add conductors, so you can step up a trade size before you order pipe.
What the Conduit Fill Tool Checks for PV Conductors
Pick your raceway and conductors and the calculator handles the Chapter 9 math:
- EMT, PVC, or RMC selection with the correct internal area
- 40 percent fill limit for three or more conductors
- PV wire and bare or insulated equipment ground counted together
- Pass or fail result with the exact fill percentage
- Trade size suggestion when the run is over the limit
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 fill percentage can I use for PV wire in roof conduit?
For a raceway with three or more conductors, NEC Chapter 9 caps fill at 40 percent. Roof heat can also force ampacity derating, so verify both the fill and the temperature adjustment against the current NEC and your local authority having jurisdiction.
Do I count the equipment ground in the fill total?
Yes. Every conductor in the raceway, including a bare or insulated equipment grounding conductor, counts toward the fill area in WireGaugeCalc.
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.