WireGaugeCalc Free calculator · NEC cited · works offline
Size Of Electrical Wire For 1 Conduit
size of electrical wire for 1 conduit is simple with WireGaugeCalc, since you pick the conduit type and trade size and enter your conductors.
The tool sums each conductor's cross-section from NEC Chapter 9 and compares it to the allowed fill area.
You see whether your wires fit before you start the pull.
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.
The 40 Percent Fill Rule For EMT, PVC, And RMC
Three or more conductors are limited to 40 percent fill, so the calculator stops you before the conduit is overstuffed.
Each conduit type has its own internal area, so EMT, PVC, and RMC of the same trade size hold different counts.
Because insulation type changes a conductor's diameter, THHN and XHHW of the same gauge fill the pipe differently.
Inputs That Set Your Conduit Fill
Tell the calculator what you are pulling:
- Conduit type, EMT, PVC, or RMC
- Trade size of the single conduit
- Conductor gauge for each wire
- Insulation type, such as THHN or XHHW
- Quantity of each conductor
- Result as fill percent 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 fill percentage is allowed for three or more conductors?
NEC Chapter 9 limits a conduit with three or more conductors to 40 percent fill. One conductor is allowed 53 percent and two are allowed 31 percent.
Does the ground wire count toward conduit fill?
Yes, the equipment grounding conductor counts toward fill just like the current-carrying conductors. Always confirm your counts and areas against the current NEC tables 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.