350 kcmil Conduit Fill by Conduit Size
How many 350 kcmil THHN conductors fit in EMT, IMC, RMC and PVC conduit, 1/2 inch through 4 inch, with the 40% fill rule applied.
Quick answer
350 kcmil conductors per conduit trade size
Same-size conductors only, at 53% for one, 31% for two and 40% for three or more.
| Conduit | 1/2" | 3/4" | 1" | 1-1/4" | 1-1/2" | 2" | 2-1/2" | 3" | 3-1/2" | 4" |
|---|---|---|---|---|---|---|---|---|---|---|
| EMT | — | — | — | 1 | 1 | 1 | 4 | 6 | 8 | 11 |
| IMC | — | — | — | 1 | 1 | 2 | 3 | 6 | 8 | 10 |
| RMC | — | — | — | 1 | 1 | 2 | 3 | 5 | 7 | 9 |
| PVC Sch 40 | — | — | — | 1 | 1 | 1 | 3 | 5 | 7 | 9 |
| PVC Sch 80 | — | — | — | 1 | 1 | 1 | 3 | 4 | 6 | 8 |
Source & method: Counts are the largest whole number where n × conductor area stays inside the raceway area times the applicable fill percentage. Mix conductor sizes in the calculator.
Fill behaviour at 350 kcmil: the most commonly pulled large size
350 kcmil is widely stocked and widely installed, so its raceway numbers are among the most useful on the site. A full set of three conductors plus a grounding conductor generally needs 3 inch raceway, and switchboard feeders at this size are frequently routed in 3 inch or 4 inch.
Where a design needs more capacity than one 350 kcmil set provides, the usual step is a second parallel set in a second raceway rather than a larger conductor. That keeps each pull manageable and lets the same termination hardware and raceway details repeat.
Source & method: Counts referenced above come from the computed table on this page — how these numbers are derived.
What each raceway type means
- EMT — EMT (electrical metallic tubing)
- IMC — IMC (intermediate metal conduit)
- RMC — RMC (rigid metal conduit)
- PVC Sch 40 — PVC Schedule 40
- PVC Sch 80 — PVC Schedule 80
Full fill charts by raceway
Per-type counts for every trade size, plus the cross-type comparison and reverse lookup.
- EMT conduit fill chart — 1/2" to 4"Electrical metallic tubing, thinnest wall, highest count per trade size.
- Conduit fill chart — all raceway types comparedEMT, IMC, RMC, PVC 40 and PVC 80 side by side with reverse lookup.
- PVC conduit fill chart — Schedule 40 and 80Thicker walls, roughly 15 to 25% fewer conductors than tubing.
- Rigid conduit fill chart — RMC and IMCThreaded metal raceway counts and usable areas.
Frequently asked
- How many 350 kcmil wires fit in 1/2 inch EMT?
- None — this size does not fit 1/2 inch EMT; step up a trade size.
- How many 350 kcmil wires fit in 3/4 inch EMT?
- 0 conductors, using a nominal THHN outside diameter of 0.817 in and the 40% fill rule for three or more conductors.
- Do neutrals and grounds count toward fill?
- Yes, every conductor in the raceway counts for fill. Grounds are excluded only from the count of current-carrying conductors used for ampacity adjustment.
- What is the cross-sectional area of 350 kcmil THHN?
- About 0.5242 square inches, from A = π × (OD / 2)² with a nominal insulated OD of 0.817 in.
More on 350 kcmil
Conduit fill for nearby sizes
Same 40% fill rule applied to the sizes either side of this one, wrapping around the range so every size is reachable.
Related charts & calculators
- Box Fill CalculatorVolume allowances for conductors, clamps, devices and grounds per NEC 314.16.
- Ampacity ChartEstimated allowable ampacity by conductor size, material and insulation rating.
- Wire Gauge ChartAWG diameter, circular mils, resistance and amp capacity in one table.
- Wire Size ChartWhat size wire for each breaker rating and typical circuit.
- kcmil Wire Size ChartMCM to AWG conversion, circular mils, resistance and ampacity for 250-750 kcmil.
- Conduit Fill ChartMaximum THHN conductors per trade size for every raceway type.