Conduit Fill Chart: How Many Wires Fit in EMT?
NEC Chapter 9 · Table 1 & Annex C · Updated 2026-07-10
The NEC limits how much of a conduit's cross-section wires may occupy: 53% for one conductor, 31% for two, and 40% for three or more (NEC Chapter 9, Table 1). The chart below answers the question electricians actually ask - how many THHN conductors fit in each trade size of EMT.
These counts come straight from the NEC's own worked-out tables (Informative Annex C, Table C.1) for THHN/THWN/THWN-2, the wire on virtually every commercial job.
EMT conduit fill chart (THHN / THWN-2, same size conductors)
| EMT size | #14 | #12 | #10 | #8 | #6 |
|---|---|---|---|---|---|
| 1/2" | 12 | 9 | 5 | 3 | 2 |
| 3/4" | 22 | 16 | 10 | 6 | 4 |
| 1" | 35 | 26 | 16 | 9 | 7 |
| 1-1/4" | 61 | 45 | 28 | 16 | 12 |
| 1-1/2" | 84 | 61 | 38 | 22 | 16 |
| 2" | 138 | 101 | 63 | 36 | 26 |
The fill percentages, and where they come from
| Situation | Max fill |
|---|---|
| 1 conductor | 53% |
| 2 conductors | 31% |
| 3 or more conductors | 40% |
| Conduit nipple ≤ 24" between enclosures | 60% |
Mixed wire sizes? Then the chart above no longer applies and you have to do the math: sum each conductor's area from Chapter 9, Table 5, and divide by the conduit's allowable area from Table 4. That's exactly the calculation the app performs live as you tap wires in - including the quirks most calculators skip, like bare-conductor dimensions for grounds and counting a multiconductor cable as a single conductor at its overall diameter.
How to check fill in the app in about five seconds
- Pick the raceway: EMT, IMC, RMC, or PVC (Schedule 40/80), 1/2" through the big stuff, against NEC 2017, 2020, 2023, or 2026 tables.
- Tap wires in: The Quick Add tray drops a wire per tap - #14 through 500 kcmil - and quick combos drop whole circuits (3φ + N + G, MWBC, 100 A feeder) in one tap.
- Read PASS or FAIL: The live cross-section packs as you go and the fill % is cited to Chapter 9 Table 1. Over the limit? Auto Size names the smallest compliant conduit. Export it as a stamped, inspector-ready PDF.
The chart, the math, and the citation - in your pocket. Conduit Fill & Bending Calc runs the full Chapter 9 calculation offline, cites every result, and exports inspector-ready PDFs. Free on the App Store. Download Conduit Fill & Bending Calc on the App Store.
Frequently asked questions
How many #12 THHN wires fit in 3/4" EMT?
Sixteen, at the 40% fill limit of NEC Chapter 9 (Annex C, Table C.1). But if more than nine of them are current-carrying you'll fail ampacity derating under 310.15(C)(1), so a practical 3/4" EMT run tops out at nine current-carrying #12s.
What is the 40% conduit fill rule?
NEC Chapter 9, Table 1 limits three or more conductors to 40% of the conduit's internal cross-sectional area. One conductor may fill 53%, two conductors 31%. The uneven numbers exist because wires nest differently in different quantities.
Do ground wires count toward conduit fill?
Yes. Every conductor - hots, neutrals, and equipment grounds - counts toward fill. Insulated grounds use their insulated dimensions from Table 5; bare grounds use the bare-conductor dimensions from Table 8, which the app applies automatically.
What is the 60% nipple rule?
A conduit nipple no longer than 24 inches installed between boxes, cabinets, or enclosures may be filled to 60% instead of 40% (Chapter 9, Notes to Tables). Ampacity adjustment factors also don't apply within the nipple.