THWN Wire Fill Chart
THWN and THWN-2 maximum conductors across every conduit type, NEC 2023. THWN-2 is the wet-rated counterpart to THHN — identical fill area.
THWN-2 is the standard wet-rated thermoplastic building wire — 90°C in both wet and dry locations. Identical Table-5 fill area as THHN. For wet locations, underground, or any raceway with moisture exposure, use THWN-2 (not single-stamp THHN). See what is THWN-2.
- 1/2" EMT9 wires
- 3/4" EMT16 wires
- 1" EMT26 wires
- 1-1/4" EMT45 wires
- 1-1/2" EMT61 wires
- 2" EMT101 wires
- 2-1/2" EMT176 wires
- 3" EMT266 wires
- 3-1/2" EMT347 wires
- 4" EMT443 wires
| TRADE → WIRE ↓ | 1/2" | 3/4" | 1" | 1-1/4" | 1-1/2" | 2" | 2-1/2" | 3" | 3-1/2" | 4" |
|---|---|---|---|---|---|---|---|---|---|---|
| 14 AWG | 12 | 22 | 35 | 61 | 84 | 138 | 241 | 364 | 476 | 608 |
| 12 AWG | 9 | 16 | 26 | 45 | 61 | 101 | 176 | 266 | 347 | 443 |
| 10 AWG | 5 | 10 | 16 | 28 | 38 | 63 | 111 | 167 | 219 | 279 |
| 8 AWG | 3 | 6 | 9 | 16 | 22 | 36 | 64 | 96 | 126 | 161 |
| 6 AWG | 2 | 4 | 7 | 12 | 16 | 26 | 46 | 69 | 91 | 116 |
| 4 AWG | — | 2 | 4 | 7 | 10 | 16 | 28 | 43 | 56 | 71 |
| 3 AWG | 1 | — | 3 | 6 | 8 | 13 | 24 | 36 | 47 | 60 |
| 2 AWG | 1 | — | 3 | 5 | 7 | 11 | 20 | 30 | 40 | 51 |
| 1 AWG | 1 | — | — | 4 | 5 | 8 | 15 | 22 | 29 | 37 |
| 1/0 | 1 | 1 | — | 3 | 4 | 7 | 12 | 19 | 25 | 32 |
| 2/0 | — | 1 | — | 2 | 3 | 6 | 10 | 16 | 20 | 26 |
| 3/0 | — | 1 | 1 | — | 3 | 5 | 8 | 13 | 17 | 22 |
| 4/0 | — | 1 | 1 | — | 2 | 4 | 7 | 11 | 14 | 18 |
| 250 | — | — | 1 | — | — | 3 | 6 | 9 | 11 | 15 |
| 300 | — | — | 1 | 1 | — | 3 | 5 | 7 | 10 | 13 |
| 350 | — | — | 1 | 1 | — | 2 | 4 | 6 | 9 | 11 |
| 400 | — | — | — | 1 | — | — | 4 | 6 | 8 | 10 |
| 500 | — | — | — | 1 | 1 | — | 3 | 5 | 6 | 8 |
| 600 | — | — | — | 1 | 1 | — | 2 | 4 | 5 | 7 |
| 700 | — | — | — | 1 | 1 | 1 | 2 | 3 | 4 | 6 |
| 750 | — | — | — | — | 1 | 1 | — | 3 | 4 | 5 |
| 800 | — | — | — | — | 1 | 1 | — | 3 | 4 | 5 |
| 900 | — | — | — | — | 1 | 1 | — | 3 | 3 | 4 |
| 1000 | — | — | — | — | 1 | 1 | — | 2 | 3 | 4 |
EMT — Electrical Metallic Tubing × THWN-2 (90°C wet/dry) · NEC 2023 Ch.9 Tables 4 & 5 · 40% (3+), 31% (2), 53% (1)
NOTES & CONTEXT
THWN vs THWN-2 vs THHN
- THWN (original): 75°C wet / 90°C dry
- THWN-2: 90°C wet AND dry — preferred for new installs
- THHN: 90°C dry-only — not permitted in wet locations
Identical NEC Table 5 area
All three insulations share identical cross-sectional area per NEC Table 5. Switching insulation type doesn't change the fill chart — only the temperature/wet rating differs. For wet-location ampacity headroom, THWN-2 gives you the 90°C column instead of 75°C.
When THWN-2 wins
- Outdoor risers, underground raceways (always wet per NEC 300.5(B))
- Conduit subject to condensation (unconditioned attics, exterior walls)
- Pool equipment circuits, hot tub feeds
- Service-entrance conductors above and below grade
Dual-stamped wire is the norm
Virtually all US building wire is sold dual-stamped: THHN/THWN-2. You get both ratings at the same price. Single-stamp THHN exists but is rarely worth the marginal cost savings.