WireGaugeCalc Free calculator · NEC cited · works offline
Racyway Fill
Racyway fill is simple with WireGaugeCalc, since you enter the conductors and the tool compares their area to the raceway limit.
It applies the Chapter 9 percentages, so three or more conductors cap at 40 percent fill.
You get the smallest compliant trade size in seconds, so the raceway pulls clean and passes inspection.
Open the calculatorEnter any two values and read the rest.
Ohm’s law: V = I × R and P = V × I. Field aid only, verify against the current NEC and your local authority having jurisdiction.
Conductor area against the allowed raceway percentage
The calculator totals the area of each conductor, so the fill check reflects exactly what goes in the raceway.
Since the allowed percentage drops with conductor count, one conductor allows 53 percent while three or more allow 40 percent.
It covers EMT, PVC, and RMC, so the result matches the method used on the job.
What the raceway fill calculation needs
Provide the conductor mix and the tool sizes the raceway:
- Conductor count, since the percentage limit depends on it
- Size and insulation type for each conductor
- Raceway type, EMT, PVC, or RMC
- Grounding conductor included in the total area
- Smallest trade size that stays under the allowed fill
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 to my raceway?
One conductor allows up to 53 percent, two allow 31 percent, and three or more cap at 40 percent. The calculator picks the right limit from the conductor count you enter.
Does the grounding conductor count toward raceway fill?
Yes, every conductor in the raceway counts, including the grounding conductor. Verify the final result against the current NEC and your local authority having jurisdiction.
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.