WireGaugeCalc Free calculator · NEC cited · works offline
Conduit Fill Calculator
conduit fill calculator work is fast with WireGaugeCalc, since you pick the raceway type and conductors and it returns the fill percentage right away.
The tool uses the conductor and raceway areas from NEC Chapter 9 so the math matches the code you are inspected against.
You get a clear pass or fail against the limit before you cut a single stick of pipe.
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 This NEC Conduit Fill Calculator Reads the Code
NEC allows 40 percent fill for three or more conductors, so the tool flags any combination that pushes past that line.
It pulls the cross-sectional area for each wire from Chapter 9 Table 5, so insulation type changes the result as it should.
Since the raceway area is fixed by trade size, adding one more conductor can move you over the limit in a single step.
What the PVC Conduit Fill Calculator Handles on the Job
Set up the run and the conduit fill calc covers the common cases you meet in the field:
- EMT, PVC, and RMC trade sizes from Chapter 9 Table 4
- One, two, or three-plus conductor fill percentages
- THHN, XHHW, and other insulation areas from Table 5
- Mixed conductor sizes in the same raceway
- A plain pass or fail against the 40 percent 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 is the maximum conduit fill percentage allowed?
For three or more conductors the NEC limit is 40 percent of the raceway cross-section. One conductor is allowed 53 percent and two conductors 31 percent. Always confirm the current NEC edition and any local amendments with your authority having jurisdiction.
Does the conductor insulation type change the fill result?
Yes, since each insulation has its own area in Chapter 9 Table 5. THHN is smaller than XHHW for the same gauge, so swapping insulation can move you over or under the limit.
Do equipment grounding conductors count toward conduit fill?
Yes, the equipment grounding conductor counts as area for fill, even bare or covered. Include it with the rest when you check the percentage.
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.