WireGaugeCalc Free calculator · NEC cited · works offline
Raceway Fill Calculator
raceway fill calculator is quick with WireGaugeCalc, since you add your conductors and the app compares their area to the raceway limit.
It uses the NEC Chapter 9 tables for wire area and the allowable fill percent for your raceway type.
That tells you whether the conductors fit before you pull them.
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.
EMT Fill Calculator Using NEC Chapter 9
The emt fill calculator pulls each conductor area from NEC Chapter 9, so mixed sizes are totaled accurately.
For three or more conductors the fill limit is 40 percent, which the app applies to EMT, PVC, and RMC.
Since the total area must stay under that limit, the calculator flags any run that is overfilled.
What The Conductor Fill Calculator Needs
To run the conductor fill check, enter these details:
- Raceway type such as EMT, PVC, or RMC
- Trade size of the raceway
- Each conductor size and insulation type
- The count of each conductor for the cable fill calculator total
- The result against the 40 percent fill 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 fill limit for more than two conductors?
For three or more conductors the limit is 40 percent of the raceway interior area, per NEC Chapter 9. Confirm the value against the current NEC and your local authority having jurisdiction.
Does insulation type change the fill result?
Yes, since THHN and XHHW have different cross sectional areas in the Chapter 9 tables. The calculator uses the area for the insulation you select.
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.