How many 12 AWG conductors fit a metric 21 (¾ inch) raceway?

Eleven 12 AWG RW90 in a metric 21 EMT, and ten in rigid PVC. Count the bonding conductor as one of them.

Does the ground wire count toward conduit fill?

Yes. A bonding conductor counts for fill. It never counts for ampacity derating under Rule 4-004 — fill and derating count differently.

What if my wires are different sizes?

Then this chart does not apply. Add up each conductor's actual area and compare it with the raceway's limit; the round-up does not apply either. The conduit fill calculator does it for you.

Is 40% the limit for everything?

No. One conductor may fill 53%, two may fill 31%, and three or more 40%. The two-conductor case is the strictest and surprises people.

🧮 Conduit Fill Chart (CEC)

US answer (NEC Annex C)

Last updated: September 16, 2026

The short answer

How many RW90 conductors of one size fit a raceway, under CEC Rule 12-910 and Table 8. Columns are metric designators: 16 is ½ inch, 21 is ¾ inch, 27 is 1 inch.

EMT

Conductor size (RW90)	16	21	27	35	41	53	63	78	91	103	129	155
14 AWG	8	14	24	42	58	96	170	200	200	200	200	200
12 AWG	6	11	18	32	44	73	130	196	200	200	200	200
10 AWG	4	8	13	23	32	54	96	145	189	200	200	200
8 AWG	2	4	7	13	18	30	53	80	105	134	185	200
6 AWG	1	3	5	9	13	22	39	60	78	100	137	198
4 AWG	1	2	4	7	9	16	28	43	56	72	99	143
3 AWG	1	2	3	6	8	13	24	36	48	61	84	121
2 AWG	1	1	2	5	6	11	20	30	40	51	70	101
1 AWG	0	1	2	3	5	8	15	23	30	38	52	75
1/0 AWG	0	1	1	3	4	7	12	19	25	31	43	63
2/0 AWG	0	0	1	2	3	6	10	16	20	26	36	53
3/0 AWG	0	0	1	2	3	4	8	13	17	22	30	44
4/0 AWG	0	0	1	1	2	4	7	11	14	18	25	36
250 kcmil	0	0	0	1	2	3	6	9	11	15	20	29
300 kcmil	0	0	0	1	1	2	5	7	10	12	17	25
350 kcmil	0	0	0	1	1	2	4	6	8	11	15	22
400 kcmil	0	0	0	1	1	2	4	6	7	10	13	20
450 kcmil	0	0	0	0	1	2	3	5	7	9	12	18

Rigid PVC

Conductor size (RW90)	16	21	27	35	41	53	63	78	91	103	129	155	200
14 AWG	7	13	22	35	51	91	133	200	200	200	200	200	200
12 AWG	5	10	17	27	39	69	101	157	200	200	200	200	200
10 AWG	4	7	12	20	29	51	75	116	156	200	200	200	200
8 AWG	2	4	7	11	16	28	41	64	87	111	176	200	200
6 AWG	1	3	5	8	12	21	31	48	64	82	130	185	200
4 AWG	1	2	3	6	8	15	22	34	46	59	94	134	200
3 AWG	1	1	3	5	7	13	19	29	39	50	80	113	200
2 AWG	0	1	2	4	6	10	15	24	33	42	67	95	169
1 AWG	0	1	2	3	4	8	11	18	24	31	50	71	126
1/0 AWG	0	1	1	2	3	6	9	15	20	26	41	59	104
2/0 AWG	0	0	1	2	3	5	8	12	17	22	35	49	87
3/0 AWG	0	0	1	1	2	4	6	10	14	18	29	41	73
4/0 AWG	0	0	0	1	2	3	5	8	11	15	24	34	60
250 kcmil	0	0	0	1	1	3	4	7	9	12	19	27	49
300 kcmil	0	0	0	1	1	2	4	6	8	10	16	24	42
350 kcmil	0	0	0	0	1	2	3	5	7	9	14	21	37
400 kcmil	0	0	0	0	1	2	3	4	6	8	13	18	33
450 kcmil	0	0	0	0	1	1	2	4	5	7	12	17	30

Each count is the raceway's internal area — derived from the internal diameters in CSA C22.1:24 Tables 9A to 9H — times the Table 8 fill limit for that number of conductors (53% for one, 31% for two, 40% for three or more), divided by the conductor area from Table 6A. Canada has no round-up allowance, so a partial conductor is simply not counted. How we verify.

Same size only

This chart is for conductors that are all the same size. Mix sizes in one raceway and you add up actual areas instead — the calculator does that. Conduit Fill calculator

Three things that change the count

RW90 is shown because it is the common jacketed building wire and the fatter of the two, so these counts are the conservative ones. T90 is thinner; the calculator offers it.

The bonding conductor takes up room and counts toward fill, even though Rule 4-004 never counts it for ampacity derating. Fill and derating count differently — that catches people out.

Rule 12-910(3) caps any single raceway at 200 conductors whatever the arithmetic says, which is why the larger sizes in this chart stop at 200.

The United States does this differently

The United States answers this with different conduit, different wire and a round-up rule, so its numbers run higher: a metric 35 raceway — the Canadian 1-1/4 inch — takes nine 6 AWG RW90, where the NEC permits twelve 6 AWG THHN in 1-1/4 inch EMT. Never carry a number across the border.

Conduit Fill calculator · Derating table · Wire ampacity chart

Common questions

How many 12 AWG conductors fit a metric 21 (¾ inch) raceway?: Eleven 12 AWG RW90 in a metric 21 EMT, and ten in rigid PVC. Count the bonding conductor as one of them.
Does the ground wire count toward conduit fill?: Yes. A bonding conductor counts for fill. It never counts for ampacity derating under Rule 4-004 — fill and derating count differently.
What if my wires are different sizes?: Then this chart does not apply. Add up each conductor's actual area and compare it with the raceway's limit; the round-up does not apply either. The conduit fill calculator does it for you.
Is 40% the limit for everything?: No. One conductor may fill 53%, two may fill 31%, and three or more 40%. The two-conductor case is the strictest and surprises people.