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Conduit Fill Calculator: NEC Chapter 9 Fill for EMT, PVC and RMC
Add every wire in the run, in any mix of sizes and THHN/THWN-2 or XHHW insulation. See the fill for every trade size at once, the smallest conduit that passes, and how many wires of one size fit.
Conduit Fill Calculator
- Wires 10.0133 sq in each0.0399 sq in
- Wires 20.0133 sq in each0.0133 sq in
| Trade size | Internal area | Allowed area | Your fill | Result |
|---|---|---|---|---|
| 1/2 in | 0.304 sq in | 0.122 sq in | 17.5% | ✓ Fits |
| 3/4 in | 0.533 sq in | 0.213 sq in | 10.0% | ✓ Fits |
| 1 in | 0.864 sq in | 0.346 sq in | 6.2% | ✓ Fits |
| 1-1/4 in | 1.496 sq in | 0.598 sq in | 3.6% | ✓ Fits |
| 1-1/2 in | 2.036 sq in | 0.814 sq in | 2.6% | ✓ Fits |
| 2 in | 3.356 sq in | 1.342 sq in | 1.6% | ✓ Fits |
| 2-1/2 in | 5.858 sq in | 2.343 sq in | 0.9% | ✓ Fits |
| 3 in | 8.846 sq in | 3.538 sq in | 0.6% | ✓ Fits |
| 3-1/2 in | 11.545 sq in | 4.618 sq in | 0.5% | ✓ Fits |
| 4 in | 14.753 sq in | 5.901 sq in | 0.4% | ✓ Fits |
Based on NEC Chapter 9 Tables 1, 4 and 5 (wire areas for THHN/THWN-2 and XHHW/XHHW-2). The one-size count applies Chapter 9 Note 7 (round up from 0.8). Fill is only one check: also apply ampacity adjustment for more than 3 current-carrying conductors, and follow the code edition your jurisdiction adopted.
How Do You Calculate Conduit Fill?
Add the area of every conductor from NEC Chapter 9 Table 5, including insulated grounds, and divide by the conduit’s internal area from Table 4. Three or more wires may fill 40%, two wires 31% and one wire 53%. For example, 3/4-inch EMT holds up to sixteen 12 AWG THHN conductors.
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EMT Conduit Fill Chart: Maximum THHN/THWN-2 Wires
Most conductors of one size allowed in EMT, from NEC Chapter 9 Tables 1, 4 and 5 (Note 7 applied).
| EMT size | 14 AWG | 12 AWG | 10 AWG | 8 AWG | 6 AWG | 4 AWG | 2 AWG | 1/0 AWG |
|---|---|---|---|---|---|---|---|---|
| 1/2 in | 12 | 9 | 5 | 3 | 1 | 1 | 1 | 0 |
| 3/4 in | 22 | 16 | 10 | 6 | 4 | 2 | 1 | 1 |
| 1 in | 35 | 26 | 16 | 9 | 7 | 4 | 3 | 1 |
| 1-1/4 in | 61 | 45 | 28 | 16 | 12 | 7 | 5 | 3 |
| 1-1/2 in | 84 | 61 | 38 | 22 | 16 | 10 | 7 | 4 |
| 2 in | 138 | 101 | 63 | 36 | 26 | 16 | 11 | 7 |
PVC Schedule 40 Conduit Fill Chart
| PVC 40 size | 14 AWG | 12 AWG | 10 AWG | 8 AWG | 6 AWG | 4 AWG | 2 AWG | 1/0 AWG |
|---|---|---|---|---|---|---|---|---|
| 1/2 in | 11 | 8 | 5 | 3 | 1 | 1 | 1 | 0 |
| 3/4 in | 21 | 15 | 9 | 5 | 4 | 1 | 1 | 1 |
| 1 in | 34 | 25 | 15 | 9 | 6 | 4 | 3 | 1 |
| 1-1/4 in | 60 | 43 | 27 | 16 | 11 | 7 | 5 | 3 |
| 1-1/2 in | 82 | 59 | 37 | 21 | 15 | 9 | 7 | 4 |
| 2 in | 135 | 99 | 62 | 36 | 26 | 16 | 11 | 7 |
Conduit Internal Area by Trade Size (NEC Table 4)
| Trade size | EMT (electrical metallic tubing) | PVC Schedule 40 | PVC Schedule 80 | Rigid metal conduit (RMC) |
|---|---|---|---|---|
| 1/2 in | 0.304 sq in | 0.285 sq in | 0.217 sq in | 0.314 sq in |
| 3/4 in | 0.533 sq in | 0.508 sq in | 0.409 sq in | 0.549 sq in |
| 1 in | 0.864 sq in | 0.832 sq in | 0.688 sq in | 0.887 sq in |
| 1-1/4 in | 1.496 sq in | 1.453 sq in | 1.237 sq in | 1.526 sq in |
| 1-1/2 in | 2.036 sq in | 1.986 sq in | 1.711 sq in | 2.071 sq in |
| 2 in | 3.356 sq in | 3.291 sq in | 2.874 sq in | 3.408 sq in |
| 2-1/2 in | 5.858 sq in | 4.695 sq in | 4.119 sq in | 4.866 sq in |
| 3 in | 8.846 sq in | 7.268 sq in | 6.442 sq in | 7.499 sq in |
| 3-1/2 in | 11.545 sq in | 9.737 sq in | 8.688 sq in | 10.010 sq in |
| 4 in | 14.753 sq in | 12.554 sq in | 11.258 sq in | 12.882 sq in |
Total internal area; multiply by 0.40 for 3 or more conductors. Always confirm with the NEC edition your jurisdiction has adopted.
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Questions
How do I calculate conduit fill?
Add up the cross-sectional area of every conductor from NEC Chapter 9, Table 5 (including insulated grounds), then compare it with the conduit’s internal area from Table 4. With three or more conductors, the total may not exceed 40% of the conduit area; one conductor may fill 53% and two conductors 31%.
How many 12 AWG THHN wires fit in 3/4 inch EMT?
Sixteen. The 40% fill area of 3/4-in EMT is 0.213 sq in, and each 12 AWG THHN is 0.0133 sq in. Remember that more than three current-carrying conductors also reduces their ampacity.
Why is the fill limit 40%?
Leaving room in the raceway lets you pull the wires without damaging the insulation and lets heat escape. The 53% and 31% limits for one and two conductors come from Chapter 9, Table 1.
Do grounding wires count toward conduit fill?
Yes. Equipment grounding and bonding conductors count toward fill. Use their actual insulation type, or Chapter 9 Table 8 for bare conductors.
What is the 60% rule for nipples?
A conduit nipple 24 inches or shorter between boxes or enclosures may be filled to 60% of its area (Chapter 9, Note 4), and ampacity adjustment for bundling does not apply to it.
What does Note 7 mean?
When all the conductors are the same size, Chapter 9 Note 7 lets you round up to the next whole conductor if the calculation ends in 0.8 or more. Our one-size count applies it.