Conduit Fill Calculator — AutoCAD 2024 Utility

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🔌 NEC Conduit Fill Calculator

Select conduit type and size, then add conductors. NEC Chapter 9, Tables 4 & 5 limits: 53% for 1 wire, 31% for 2 wires, 40% for 3+ wires.

Conduit Type

Conduit Size

Conduit Internal Area From NEC Chapter 9, Table 4

Conductors

NEC Fill Limits Reference

NEC Chapter 9, Table 1: 1 conductor = 53% max fill · 2 conductors = 31% max fill · 3+ conductors = 40% max fill. These limits apply to all conduit types. Derating for more than 3 current-carrying conductors in a raceway per NEC 310.15(C)(1).

Conduit Size	Type	Total Area (in²)	40% Fill (in²)	31% Fill (in²)	53% Fill (in²)

THHN/THWN Wire Areas (NEC Ch. 9, Table 5)

AWG / kcmil	Area (in²)	Diameter (in)	Common Use
#14	0.0097	0.111	15A circuits, control wiring
#12	0.0133	0.130	20A circuits, general purpose
#10	0.0211	0.164	30A circuits, HVAC feeders
#8	0.0366	0.216	40–50A, dryers, small feeders
#6	0.0507	0.254	55–65A, panel feeders
#4	0.0824	0.324	70–85A, sub-panel feeders
#3	0.0973	0.352	85–100A feeders
#2	0.1158	0.384	95–115A, service entrance
#1	0.1562	0.446	110–130A, large feeders
#1/0	0.1855	0.486	125–150A, service entrance
#2/0	0.2223	0.532	145–175A, main feeders
#3/0	0.2679	0.584	165–200A, main feeders
#4/0	0.3237	0.642	195–230A, service entrance
250 kcmil	0.3970	0.711	215–255A, large service
300 kcmil	0.4608	0.766	240–285A, large service
350 kcmil	0.5242	0.817	260–310A, large feeders
400 kcmil	0.5863	0.864	280–335A
500 kcmil	0.7073	0.949	320–380A, large feeders
600 kcmil	0.8659	1.051	355–420A
750 kcmil	1.0496	1.156	400–475A, utility primary

🔌 Conduit Fill Calculator