WireGaugeCalc Free calculator · NEC cited · works offline
Carlon Box Fill Calculator
Carlon box fill calculator is simple with WireGaugeCalc, since you enter the raceway size and the conductors and the app returns the fill percentage.
The calculator applies the NEC Chapter 9 tables, so a run with three or more conductors is checked against the 40% fill limit.
You see whether the Carlon PVC or EMT run is within code before you pull, so you avoid a redo.
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.
How The 40% Fill Limit Applies
When a raceway holds three or more conductors, NEC limits total cross section to 40% of the inside area.
WireGaugeCalc sums each conductor area and compares it to the trade size you picked, so you know if the PVC is full.
Since fill changes with conductor count and gauge, the app updates the percentage as you adjust the run.
Checking PVC And EMT Conduit Fill
The calculator covers the inputs that drive fill:
- Carlon PVC, EMT, and RMC trade sizes
- Conductor count and gauge per the Chapter 9 tables
- 40% fill limit for three or more conductors
- Insulation type so the conductor area is correct
- Clear pass or over-fill result before the pull
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
Does the 40% fill rule apply to Carlon PVC?
Yes, the 40% limit applies to any raceway with three or more conductors, including Carlon PVC, EMT, and RMC. Confirm the exact areas against the current NEC Chapter 9 and your local authority having jurisdiction.
Why does fill change when I switch insulation type?
Each insulation has a different overall conductor area, so THHN and XHHW of the same gauge take different room, and the calculator adjusts the fill to match.
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.