Conduit fill chart

Name: Conduit fill chart
Creator: Calculate.diy

3/4 inch EMT holds up to 16 wires of 12 AWG THHN or 10 wires of 10 AWG, and 1/2 inch EMT holds 9 wires of 12 AWG, at the 40% fill limit for three or more conductors.

Electrical metallic tubing (EMT): maximum THHN wires

Maximum number of THHN wires of each size in Electrical metallic tubing (EMT) by trade size, at 40% fill for three or more wires
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	1	4	7	12	16	26	46	69	91	116
4 AWG	1	2	4	7	10	16	28	43	56	71
3 AWG	1	1	3	6	8	13	24	36	47	60
2 AWG	1	1	3	5	7	11	20	30	40	51
1 AWG	1	1	1	4	5	8	15	22	29	37
1/0 AWG	—	1	1	3	4	7	12	19	25	32
2/0 AWG	—	1	1	2	3	6	10	16	20	26
3/0 AWG	—	1	1	1	3	5	8	13	17	22
4/0 AWG	—	—	1	1	1	4	7	11	14	18

Rigid PVC conduit, Schedule 40: maximum THHN wires

Maximum number of THHN wires of each size in Rigid PVC conduit, Schedule 40 by trade size, at 40% fill for three or more wires
Wire	1/2″	3/4″	1″	1-1/4″	1-1/2″	2″	2-1/2″	3″	3-1/2″	4″
14 AWG	11	21	34	60	82	135	193	299	401	517
12 AWG	8	15	25	43	59	99	141	218	293	377
10 AWG	5	9	15	27	37	62	89	137	184	238
8 AWG	3	5	9	16	21	36	51	79	106	137
6 AWG	1	4	6	11	15	26	37	57	77	99
4 AWG	1	1	4	7	9	16	22	35	47	61
3 AWG	1	1	3	6	8	13	19	30	40	51
2 AWG	1	1	3	5	7	11	16	25	33	43
1 AWG	—	1	1	3	5	8	12	18	25	32
1/0 AWG	—	1	1	3	4	7	10	15	21	27
2/0 AWG	—	1	1	2	3	6	8	13	17	22
3/0 AWG	—	1	1	1	3	5	7	11	14	18
4/0 AWG	—	—	1	1	1	4	6	9	12	15

Rigid PVC conduit, Schedule 80: maximum THHN wires

Maximum number of THHN wires of each size in Rigid PVC conduit, Schedule 80 by trade size, at 40% fill for three or more wires
Wire	1/2″	3/4″	1″	1-1/4″	1-1/2″	2″	2-1/2″	3″	3-1/2″	4″
14 AWG	9	17	28	51	70	118	170	265	358	464
12 AWG	6	12	20	37	51	86	124	193	261	338
10 AWG	4	7	13	23	32	54	78	122	164	213
8 AWG	1	4	7	13	18	31	45	70	95	123
6 AWG	1	3	5	9	13	22	32	51	68	89
4 AWG	1	1	3	6	8	14	20	31	42	54
3 AWG	1	1	3	5	7	12	17	26	35	46
2 AWG	—	1	1	4	6	10	14	22	30	39
1 AWG	—	1	1	3	4	7	10	16	22	29
1/0 AWG	—	1	1	2	3	6	9	14	18	24
2/0 AWG	—	—	1	1	3	5	7	11	15	20
3/0 AWG	—	—	1	1	1	4	6	9	13	17
4/0 AWG	—	—	1	1	1	3	5	8	10	14

Rigid metal conduit (RMC): maximum THHN wires

Maximum number of THHN wires of each size in Rigid metal conduit (RMC) by trade size, at 40% fill for three or more wires
Wire	1/2″	3/4″	1″	1-1/4″	1-1/2″	2″	2-1/2″	3″	3-1/2″	4″
14 AWG	13	22	36	63	85	140	200	309	412	531
12 AWG	9	16	26	46	62	102	146	225	301	387
10 AWG	6	10	17	29	39	64	92	142	189	244
8 AWG	3	6	9	16	22	37	53	82	109	140
6 AWG	1	4	7	12	16	27	38	59	79	101
4 AWG	1	2	4	7	10	16	23	36	48	62
3 AWG	1	1	3	6	8	14	20	31	41	53
2 AWG	1	1	3	5	7	11	17	26	34	44
1 AWG	1	1	1	4	5	8	12	19	25	33
1/0 AWG	—	1	1	3	4	7	10	16	21	27
2/0 AWG	—	1	1	2	3	6	8	13	18	23
3/0 AWG	—	1	1	1	3	5	7	11	15	19
4/0 AWG	—	—	1	1	1	4	6	9	12	16

How the conduit fill chart is calculated

Each number is the inside area of the conduit times the fill limit, divided by the area of one THHN/THWN-2 wire. The limit is 40% for three or more wires, 31% for two and 53% for one. When all wires are one size, a result with a decimal of 0.8 or more is rounded up. Ground wires count toward the total.

The chart is about physical fill only. More than three current-carrying wires in one conduit must be derated, and a mix of sizes needs the conduit fill calculator.

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Sources

NFPA 70, National Electrical Code (2023): Percent of cross section of conduit and tubing for conductors, Chapter 9 Table 1
NFPA 70, National Electrical Code (2023): Dimensions and percent area of conduit and tubing, Chapter 9 Table 4
NFPA 70, National Electrical Code (2023): Dimensions of insulated conductors, Chapter 9 Table 5

Compared with 4 published documents, last on 2026-11-13

Carlon / Thomas & Betts (ABB) (catalog (edition not stated)): General information: wire fill based on Chapter 9 Table 1 — Conduit fill percentages
Florida International University (course notes, NEC edition not stated): Chapter III, Electrical Wiring Components (Figure 3.18, area of THHN conductors) — THHN areas for 14 to 6 AWG; the larger sizes match a training reproduction of the same table
Southwire Company, Power Cable Installation Guide (2005 (cites 2005 NEC)): Dimensions and percent area of conduit and tubing, Table 8 (EMT, rigid PVC Schedule 40 and 80) — Fill percentages and internal areas of EMT, PVC Schedule 40 and Schedule 80
Wheatland Tube (2022): Rigid Metal Conduit Submittal Sheet, weights and dimensions — Rigid metal conduit inside diameters; the areas follow from them

Calculated by Calculate.diy with the method of the National Electrical Code® (NEC®), 2023 edition; not the NEC text. Methodology. For planning only: check local code and use a licensed electrician.