NEC Chapter 9 Table 5 Conductor Dimensions
NEC Chapter 9 Table 5 gives cross-sectional area for every insulated conductor type. Includes THHN, THWN-2, XHHW, RHH/RHW, TW from 14 AWG through 1000 kcmil.
NEC Chapter 9 Table 5 of NFPA 70 (2023) lists approximate cross-sectional area for every common insulated conductor type at every standard AWG and kcmil size. The table is the second half of the conduit fill calculation: multiply the count of each conductor by its Table 5 area, sum, and compare against Table 4 multiplied by the Table 1 fill percentage. Get Table 5 right and the rest is arithmetic.
How Table 5 Is Organized
The full table runs from 18 AWG fixture wire through 2000 kcmil power cable. Columns are grouped by insulation family:
- TBS, SA, SIS, FEP, FEPB, PFA, RHH, RHW, RHW-2, THHW, THW, THW-2
- TFE, PFAH, Z
- TW
- TFN, TFFN
- THHN, THWN, THWN-2, MTW
- XHHW, XHHW-2, ZW
For practical conduit work, the THHN/THWN-2 column and the XHHW column are by far the most-used. RHH/RHW comes up in older buildings and some industrial work; TW shows up in cord and direct-buried legacy systems.
Conductor Areas (in^2) - Most-Used Insulations
| Size | THHN / THWN-2 | XHHW | RHH / RHW (no jacket) | TW |
|---|---|---|---|---|
| 14 AWG | 0.0097 | 0.0139 | 0.0209 | 0.0139 |
| 12 AWG | 0.0133 | 0.0181 | 0.0260 | 0.0181 |
| 10 AWG | 0.0211 | 0.0243 | 0.0333 | 0.0243 |
| 8 AWG | 0.0366 | 0.0437 | 0.0556 | 0.0437 |
| 6 AWG | 0.0507 | 0.0590 | 0.0726 | 0.0726 |
| 4 AWG | 0.0824 | 0.0814 | 0.0973 | 0.0973 |
| 3 AWG | 0.0973 | 0.0962 | 0.1134 | 0.1134 |
| 2 AWG | 0.1158 | 0.1146 | 0.1333 | 0.1333 |
| 1 AWG | 0.1562 | 0.1534 | 0.1901 | 0.1901 |
| 1/0 | 0.1855 | 0.1825 | 0.2223 | 0.2223 |
| 2/0 | 0.2223 | 0.2190 | 0.2624 | 0.2624 |
| 3/0 | 0.2679 | 0.2642 | 0.3117 | 0.3117 |
| 4/0 | 0.3237 | 0.3197 | 0.3718 | 0.3718 |
| 250 kcmil | 0.3970 | 0.3904 | 0.4596 | 0.4596 |
| 300 kcmil | 0.4608 | 0.4536 | 0.5281 | 0.5281 |
| 350 kcmil | 0.5242 | 0.5166 | 0.5958 | 0.5958 |
| 400 kcmil | 0.5863 | 0.5782 | 0.6619 | 0.6619 |
| 500 kcmil | 0.7073 | 0.6984 | 0.7901 | 0.7901 |
| 600 kcmil | 0.8676 | 0.8709 | 0.9729 | - |
| 750 kcmil | 1.0496 | 1.0532 | 1.1882 | - |
| 1000 kcmil | 1.3478 | 1.3478 | 1.5482 | - |
Values are from NEC 2023 Chapter 9 Table 5. Note that at small sizes (14 - 4 AWG) the THHN/THWN-2 column is the smallest of the four; at large sizes the differences narrow because the conductor metal dominates and the insulation jacket is a smaller percentage of overall diameter.
Why Insulation Type Matters
- THHN / THWN-2 uses thin nylon jacket over PVC insulation - the most compact mainstream insulation
- XHHW / XHHW-2 uses cross-linked polyethylene without a separate jacket - slightly bulkier than THHN at small sizes, equal at large
- RHH / RHW uses thermoset rubber - heaviest insulation, common in legacy industrial
- TW uses thick PVC without nylon jacket - rated only 60C
For modern installations, THHN/THWN-2 dominates because it lets you fit more conductors per conduit. See deep dives at THHN, THWN-2, XHHW, and RHH.
Worked Example
Goal: Fit 6 x 4/0 THHN + 1 x 2 AWG THHN EGC in EMT.
- 6 x 4/0 THHN = 6 x 0.3237 = 1.9422 in^2
- 1 x 2 AWG THHN = 0.1158 in^2
- Total = 2.058 in^2
Need EMT interior area at 40% fill of at least 2.058 in^2. Table 4 EMT: 2" = 1.342 in^2, 2-1/2" = 2.343 in^2. 2-1/2" EMT is the minimum. (For RMC the answer changes - 2-1/2" RMC has only 1.946 in^2 at 40%, so you would need 3" RMC.)
Common Pitfalls
- Looking up the wrong column. XHHW and THHN are not identical at every size - check the column header carefully.
- Forgetting EGC area. The equipment grounding conductor is a conductor for fill purposes. A 6-circuit feeder with 6 hots, 6 neutrals, and 1 EGC has 13 conductors in the fill calculation.
- Using bare conductor area. Table 5 is for insulated conductors. Bare conductors (for example, bare equipment grounding) use Table 8 dimensions.
Cross-References
- NEC Chapter 9 Table 5A - compact aluminum dimensions
- NEC Chapter 9 Table 8 - bare conductor dimensions (use for bare EGC)
- Annex C - pre-computed fill counts for identical conductors
- NEC Chapter 9 Table 1 - the fill percentages
- NEC Chapter 9 Table 4 - conduit interior areas; see Table 4 guide
How WireFillChart Implements It
Our conduit fill calculator stores the full Table 5 dataset for every insulation type from 14 AWG to 1000 kcmil. Mix and match insulations - the calculator multiplies each conductor's individual area and sums correctly. Bare EGCs reference Table 8. For background, see AWG explained and kcmil explained.