WireGaugeCalc Free calculator · NEC cited · works offline
Conduit Size For 4 Gauge Wire
conduit size for 4 gauge wire is simple with WireGaugeCalc, since you enter the conductor count and the tool returns the smallest legal raceway.
It applies the NEC Chapter 9 area tables and the 40 percent fill limit, so the trade size you get clears the code.
The payoff is the right EMT, PVC, or RMC before you ever cut a stick.
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 The 40 Percent Fill Rule Sets The Trade Size
Three or more conductors are limited to 40 percent of the raceway interior, so each 4 AWG conductor uses a fixed area.
EMT, PVC, and RMC have different inside diameters, as the wall thickness changes per type.
The tool sums the conductor areas, then picks the first trade size that stays under the 40 percent line.
Inputs For 4 AWG In EMT, PVC, Or RMC
Give the tool a few details and it sizes the raceway:
- Number of 4 AWG conductors in the run
- Insulation type, such as THHN or XHHW, which sets the wire area
- Conduit type, EMT, PVC, or RMC
- Applies the NEC Chapter 9 fill tables
- Holds the run to the 40 percent fill limit
- Returns the smallest compliant trade size
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 size conduit fits three 4 AWG THHN conductors?
Three 4 AWG THHN typically land in 3/4 inch EMT under the 40 percent rule, since their combined area stays below the limit. Check the exact area against the current NEC Chapter 9 tables and your local authority having jurisdiction.
Does adding a ground change the conduit size?
Yes, the equipment grounding conductor counts toward fill, so its area is added before the trade size is chosen. A larger ground can push you up to the next size.
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.