WireGaugeCalc Free calculator · NEC cited · works offline
Multiconductor Conduit Fill
Multiconductor conduit fill is simple with WireGaugeCalc, since you add each conductor by size and insulation and the tool totals the area used.
It applies the NEC Chapter 9 limit, 40% for three or more conductors, and reports whether your EMT, PVC, or RMC has the room.
So a raceway packed with several wires gets checked in one pass instead of by hand.
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.
Adding Up Conductors in One Raceway
Each conductor takes a fixed cross-sectional area from Chapter 9, so the calculator sums them and compares the total to the conduit's inside area.
Since three or more conductors cap fill at 40%, the tool uses that limit by default and shows the percent used.
It handles mixed sizes in the same run, so a feeder plus a few small conductors is counted accurately.
Inputs for an EMT or PVC Run
Tell the calculator what is going in the pipe and it returns the fill percentage:
- Conduit type, EMT, PVC, or RMC
- Trade size of the conduit
- Each conductor size and count
- Insulation type, such as THHN or XHHW
- The 40% limit applied automatically
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 applies when I have several conductors in one conduit?
For three or more conductors, the NEC Chapter 9 limit is 40% of the conduit's interior area. The calculator uses that figure unless your case calls for a different one. Confirm against the current NEC and your local authority having jurisdiction.
Do the conductors all have to be the same size to count them together?
No, you can mix sizes in the same raceway, and the tool sums each conductor's own area, since fill is based on total cross-section rather than count alone.
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.