What is the maximum conduit fill in Canada?

CEC Rule 12-910 and Table 8 limit fill to 53% for one conductor, 31% for two and 40% for three or more (60% for nipples up to 600 mm), the same percentages as the NEC.

Does the CEC have a 360° bend limit?

Yes. Rule 12-942 limits bends between pull points to the equivalent of four quarter bends (360° total).

Do bonding conductors count toward conduit fill?

Yes. Bare or insulated bonding (grounding) conductors take up space and must be included in the fill calculation, though they do not count as current-carrying conductors for derating.

Which conductor dimensions are used?

The calculator uses THHN/T90 Nylon insulated areas (NEC Chapter 9 Table 5) and nominal conduit internal areas for EMT, rigid PVC and rigid metal conduit. CEC 2024 Tables 6A–6K and 9A–9P are not publicly available, so treat results as an estimate and confirm against the code book. Check your manufacturer's data for other insulation types such as RW90.

How many 12 AWG T90 conductors fit in 1/2 inch EMT?

Nine, at the 40% fill limit for three or more conductors. 3/4 in EMT holds 16.

Conduit Fill Calculator Canada (CEC 12-910)

Apply the CEC Rule 12-910 fill limits to EMT, rigid PVC and rigid metal conduit. Enter your conductors and the calculator shows the fill and the smallest conduit that works.

CEC data notice: CEC values were checked against public summaries of CSA C22.1:24, not the code book itself. Conduit and conductor areas use NEC Chapter 9 data, and some aluminum kcmil ampacities are unverified. Confirm against the CEC edition and provincial amendments adopted where you work.

CEC fill limits

CEC Rule 12-910 refers to Table 8 for the maximum percentage of conduit cross-section conductors may occupy:

Number of conductors	Maximum fill
1	53%
2	31%
3 or more	40%

Two conductors get the lowest limit because two round conductors can jam across the conduit diameter during a pull. Bare and insulated bonding conductors count toward fill.

The calculation

Fill % = (sum of conductor areas) ÷ (conduit internal area) × 100

Each conductor's area is π × d² ÷ 4 using its overall diameter including insulation. Add them up, divide by the conduit's internal area, and compare with the limit.

Worked examples

1. Three 20 A circuits in 3/4 in EMT

Six 12 AWG T90 Nylon (0.0133 in², about 8.6 mm² each) plus one 10 AWG bond (0.0211 in²): total 0.1009 in². 3/4 in EMT has 0.533 in² internal area:

0.1009 ÷ 0.533 = 18.9%

Well under 40%. In 1/2 in EMT (0.304 in²) the same bundle is 33.2%, still allowed, although a 3/4 in pull is much easier.

2. A 60 A feeder

Three 6 AWG (0.0507 in² each) plus a 10 AWG bond: 0.1732 in². In 1/2 in EMT that is 57%, over the limit. In 3/4 in EMT it is 32.5%, which complies.

3. A 200 A feeder in rigid PVC

Four 3/0 (0.2679 in² each) plus a 4 AWG bond (0.0824 in²) total 1.154 in². The smallest rigid PVC that keeps this under 40% is 2 in, at 35.1%.

Other Canadian rules to keep in mind

Bends. Rule 12-942: no more than the equivalent of four quarter bends between pull points.
Derating. More than three current-carrying conductors in a raceway reduces ampacity under Rule 4-004 and Table 5C. See the ampacity derating page (NEC values, similar in principle).
Expansion. Rigid PVC exposed to temperature change needs expansion joints per Rule 12-1118.
Voltage drop. Rule 8-102 limits feeders and branch circuits to 3%. Check long runs with the Canadian voltage drop calculator.

Tips for easier pulls

Staying at 40% does not guarantee an easy pull. Long runs with several bends, or jam-ratio combinations of three conductors, can damage insulation. Many electricians aim for 30–35% on long runs and use the next size up for future capacity. Pulling lubricant helps, and so does pulling from the end nearest the bends.

For US installations, use the NEC conduit fill calculator, which uses the same percentages with NEC Chapter 9 tables.

Conduit Fill Calculator (Canada, CEC)