Canadian EMT Conduit Fill Chart
Free Calculator and Full Tables (CEC 2026)
A practical conduit fill reference for Canadian electricians and contractors. Covers EMT, PVC Schedule 40, and RMC with complete THWN and RW90 conductor tables, a working fill calculator, and a free printable PDF.
CEC Rule 12-910 Compliant
EMT · PVC Sch 40 · RMC
14 AWG to 500 kcmil
THWN / RW90 / TWN75
Free PDF Download
Interactive Calculator
EMT · PVC Sch 40 · RMC
14 AWG to 500 kcmil
THWN / RW90 / TWN75
Free PDF Download
Interactive Calculator
The Three Fill Rules: CEC Rule 12-910 and NEC Chapter 9
Canada’s CEC Rule 12-910 and the US NEC Chapter 9, Table 1 use the same fill limits. These percentages apply to the conduit’s total internal cross-sectional area and prevent overheating, protect insulation during pulling, and leave room for future work.
53%
1 Conductor
Used for service entrances, large feeders, and single dedicated circuits. A higher fill is allowed because one conductor dissipates heat more effectively.
31%
2 Conductors
Applies to 240V runs, two-wire circuits, and two-conductor feeders. The tighter limit reflects the added difficulty of pulling two conductors.
40%
3+ Conductors
Standard branch circuits, multi-wire homeruns, and control wiring. Most commercial conduit runs fall under this rule.
📌 Nipple rule: Conduit sections 600 mm (24 inches) or less can be filled to 60%. These short sections connecting panels, junction boxes, or equipment enclosures are called nipples under the CEC. This does not apply to standard conduit runs.
⚠️ Long runs: The code allows 40%, but most installers target 30% or less on runs with four or more bends or over 25 metres. High fill in a conduit with multiple bends puts real stress on insulation and makes future additions difficult.
Canadian Wire Types: CEC vs NEC Equivalents
Canadian wire designations differ from US equivalents, but the cross-sectional areas are the same. RW90 is the standard commercial building wire in Canada and is equivalent to THHN/THWN-2. Use the same fill values for both.
| Canadian Wire Type (CEC) | US NEC Equivalent | Temperature Rating | Typical Application |
|---|---|---|---|
| RW90 / RW90XLPE | THHN / THWN-2 | 90°C wet & dry | General commercial and industrial use, most common in Canada |
| TWN75 | THWN | 75°C wet, 90°C dry | General purpose, common in existing installations |
| T90 Nylon | THHN | 90°C dry only | Dry locations and conduit runs only, not rated for wet areas |
| TW | TW | 60°C wet & dry | Older residential and low-temperature applications |
| RW75 | XHHW | 75°C wet, 90°C dry | Feeders and service entrances |
✅ Bottom line: Specifying RW90? Use the THWN/THHN values in these tables. The cross-sectional areas are the same and all calculations apply directly.
Free Conduit Fill Calculator
Choose conduit type and size, select the wire gauge, then enter the number of conductors. Results show the maximum allowed count and your actual fill percentage.
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Max Conductors Allowed
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Your Actual Fill %
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Available Fill Area (in²)
Complete Conduit Fill Tables: 40% Fill (3 or More Conductors)
Maximum conductors at 40% fill for THWN, RW90, and TWN75. Wire areas from NEC Chapter 9, Table 5. Formula: floor(conduit area × 0.40 ÷ wire area).
EMT: Small Wire
EMT: Large Wire
PVC Sch 40: Small Wire
PVC Sch 40: Large Wire
RMC: Small Wire
| Wire Size | ½” EMT | ¾” EMT | 1″ EMT | 1¼” EMT | 1½” EMT | 2″ EMT | 2½” EMT | 3″ EMT | 3½” EMT | 4″ EMT |
|---|---|---|---|---|---|---|---|---|---|---|
| 14 AWG | 12 | 21 | 35 | 61 | 83 | 138 | 241 | 364 | 475 | 608 |
| 12 AWG | 9 | 16 | 25 | 44 | 61 | 100 | 176 | 266 | 347 | 443 |
| 10 AWG | 5 | 10 | 16 | 28 | 38 | 63 | 111 | 167 | 218 | 279 |
| 8 AWG | 3 | 5 | 9 | 16 | 22 | 36 | 64 | 96 | 126 | 161 |
| 6 AWG | 2 | 4 | 6 | 11 | 16 | 26 | 46 | 69 | 91 | 116 |
| 4 AWG | 1 | 2 | 4 | 7 | 9 | 16 | 28 | 42 | 56 | 71 |
| 3 AWG | 1 | 2 | 3 | 6 | 8 | 13 | 24 | 36 | 47 | 60 |
| 2 AWG | 1 | 1 | 2 | 5 | 7 | 11 | 20 | 30 | 39 | 50 |
| Wire Size | ½” EMT | ¾” EMT | 1″ EMT | 1¼” EMT | 1½” EMT | 2″ EMT | 2½” EMT | 3″ EMT | 3½” EMT | 4″ EMT |
|---|---|---|---|---|---|---|---|---|---|---|
| 1 AWG | — | 1 | 2 | 3 | 5 | 8 | 15 | 22 | 29 | 37 |
| 1/0 AWG | — | 1 | 1 | 3 | 4 | 7 | 12 | 19 | 24 | 31 |
| 2/0 AWG | — | — | 1 | 2 | 3 | 6 | 10 | 15 | 20 | 26 |
| 3/0 AWG | — | — | 1 | 2 | 3 | 5 | 8 | 13 | 17 | 22 |
| 4/0 AWG | — | — | 1 | 1 | 2 | 4 | 7 | 10 | 14 | 18 |
| 250 kcmil | — | — | — | 1 | 2 | 3 | 5 | 8 | 11 | 14 |
| 300 kcmil | — | — | — | 1 | 1 | 2 | 5 | 7 | 10 | 12 |
| 350 kcmil | — | — | — | 1 | 1 | 2 | 4 | 6 | 8 | 11 |
| 400 kcmil | — | — | — | — | 1 | 2 | 3 | 5 | 7 | 9 |
| 500 kcmil | — | — | — | — | 1 | 1 | 3 | 4 | 6 | 8 |
| Wire Size | ½” PVC | ¾” PVC | 1″ PVC | 1¼” PVC | 1½” PVC | 2″ PVC | 2½” PVC | 3″ PVC | 3½” PVC | 4″ PVC |
|---|---|---|---|---|---|---|---|---|---|---|
| 14 AWG | 12 | 22 | 36 | 62 | 85 | 140 | 200 | 308 | 412 | 531 |
| 12 AWG | 9 | 16 | 26 | 45 | 62 | 102 | 146 | 224 | 300 | 387 |
| 10 AWG | 5 | 10 | 16 | 28 | 39 | 64 | 92 | 141 | 189 | 243 |
| 8 AWG | 3 | 5 | 9 | 16 | 22 | 37 | 53 | 81 | 109 | 140 |
| 6 AWG | 2 | 4 | 6 | 12 | 16 | 26 | 38 | 59 | 79 | 101 |
| 4 AWG | 1 | 2 | 4 | 7 | 10 | 16 | 23 | 36 | 48 | 62 |
| 3 AWG | 1 | 2 | 3 | 6 | 8 | 14 | 20 | 30 | 41 | 52 |
| 2 AWG | 1 | 1 | 3 | 5 | 7 | 11 | 16 | 25 | 34 | 44 |
ℹ️ PVC Schedule 40 has a slightly larger internal diameter than EMT in most sizes, allowing marginally more conductors in the same trade size. PVC Sch 40 is common for underground and outdoor runs in Canada.
| Wire Size | ½” PVC | ¾” PVC | 1″ PVC | 1¼” PVC | 1½” PVC | 2″ PVC | 2½” PVC | 3″ PVC | 3½” PVC | 4″ PVC |
|---|---|---|---|---|---|---|---|---|---|---|
| 1 AWG | — | 1 | 2 | 3 | 5 | 8 | 12 | 19 | 25 | 32 |
| 1/0 AWG | — | 1 | 1 | 3 | 4 | 7 | 10 | 16 | 21 | 27 |
| 2/0 AWG | — | — | 1 | 2 | 3 | 6 | 8 | 13 | 18 | 23 |
| 3/0 AWG | — | — | 1 | 2 | 3 | 5 | 7 | 11 | 15 | 19 |
| 4/0 AWG | — | — | 1 | 1 | 2 | 4 | 5 | 9 | 12 | 15 |
| 250 kcmil | — | — | — | 1 | 2 | 3 | 4 | 7 | 9 | 12 |
| 300 kcmil | — | — | — | 1 | 1 | 2 | 4 | 6 | 8 | 11 |
| 350 kcmil | — | — | — | 1 | 1 | 2 | 3 | 5 | 7 | 9 |
| 400 kcmil | — | — | — | — | 1 | 2 | 3 | 5 | 6 | 8 |
| 500 kcmil | — | — | — | — | 1 | 1 | 2 | 4 | 5 | 7 |
| Wire Size | ½” RMC | ¾” RMC | 1″ RMC | 1¼” RMC | 1½” RMC | 2″ RMC | 2½” RMC | 3″ RMC | 3½” RMC | 4″ RMC |
|---|---|---|---|---|---|---|---|---|---|---|
| 14 AWG | 12 | 22 | 36 | 62 | 85 | 140 | 224 | 332 | 439 | 560 |
| 12 AWG | 9 | 16 | 26 | 45 | 62 | 102 | 163 | 242 | 320 | 408 |
| 10 AWG | 5 | 10 | 16 | 28 | 39 | 64 | 103 | 153 | 202 | 258 |
| 8 AWG | 3 | 5 | 9 | 16 | 22 | 37 | 59 | 88 | 116 | 148 |
| 6 AWG | 2 | 4 | 6 | 12 | 16 | 26 | 43 | 63 | 84 | 107 |
| 4 AWG | 1 | 2 | 4 | 7 | 10 | 16 | 26 | 39 | 51 | 66 |
| 3 AWG | 1 | 2 | 3 | 6 | 8 | 14 | 22 | 33 | 43 | 55 |
| 2 AWG | 1 | 1 | 3 | 5 | 7 | 11 | 18 | 27 | 36 | 46 |
ℹ️ Rigid Metal Conduit (RMC) has the thickest walls of the three types, giving it a smaller internal area than PVC Sch 40 of the same trade size. RMC is required in high-exposure locations and where maximum mechanical protection is needed.
Conduit Internal Dimensions and 40% Fill Area: Quick Reference
| Trade Size | EMT Total Area (in²) | EMT 40% Fill (in²) | PVC Sch 40 Total (in²) | PVC 40% Fill (in²) | RMC Total Area (in²) | RMC 40% Fill (in²) |
|---|---|---|---|---|---|---|
| ½” | 0.304 | 0.122 | 0.314 | 0.126 | 0.314 | 0.126 |
| ¾” | 0.533 | 0.213 | 0.549 | 0.220 | 0.549 | 0.220 |
| 1″ | 0.864 | 0.346 | 0.887 | 0.355 | 0.887 | 0.355 |
| 1¼” | 1.496 | 0.598 | 1.526 | 0.610 | 1.526 | 0.610 |
| 1½” | 2.036 | 0.814 | 2.071 | 0.828 | 2.071 | 0.828 |
| 2″ | 3.356 | 1.342 | 3.408 | 1.363 | 3.408 | 1.363 |
| 2½” | 5.858 | 2.343 | 4.866 | 1.946 | 5.452 | 2.181 |
| 3″ | 8.846 | 3.538 | 7.475 | 2.990 | 8.085 | 3.234 |
| 3½” | 11.545 | 4.618 | 10.010 | 4.004 | 10.694 | 4.278 |
| 4″ | 14.753 | 5.901 | 12.882 | 5.153 | 13.631 | 5.452 |
Calculating Conduit Fill with Mixed Wire Sizes
Mixed gauges are common in commercial work. A typical circuit homerun carries two 12 AWG hots, a 12 AWG neutral, and a 14 AWG ground. The process is the same regardless of the combination:
Step-by-step example
Step 1: List every conductor and its cross-sectional area.
| Conductor | Wire Size | Area per Wire (in²) | Quantity | Total Area (in²) |
|---|---|---|---|---|
| Hot (Phase A) | 12 AWG THWN | 0.0133 | 1 | 0.0133 |
| Hot (Phase B) | 12 AWG THWN | 0.0133 | 1 | 0.0133 |
| Neutral | 12 AWG THWN | 0.0133 | 1 | 0.0133 |
| Equipment Ground | 14 AWG THWN | 0.0097 | 1 | 0.0097 |
| Total conductor area: | 0.0496 in² | |||
Step 2: Four conductors means 40% fill applies.
Step 3: Find a conduit where 40% of the internal area is at least 0.0496 in².
½” EMT: 0.304 × 0.40 = 0.122 in² → 0.122 is greater than 0.0496. ✅ ½” EMT passes.
✅ Result: This 4-conductor combination fits in ½” EMT at 40% fill. Actual fill is 16.3%, well within limits and with room for a future wire.
📌 Ground wires count for fill: EGCs must be included in fill calculations even though they are excluded from ampacity derating. A common mistake is to leave them out.
Conduit Fill and Ampacity Derating: What Changes at 4+ Conductors
Fill percentage and ampacity derating are separate calculations that use different conductor counts. When four or more current-carrying conductors share a conduit, CEC Table 5C and NEC 310.15 require ampacity derating because bundled conductors trap heat.
| Current-Carrying Conductors in Conduit | Ampacity Derating Factor | Example: 12 AWG RW90 (30A) Becomes |
|---|---|---|
| 1–3 conductors | 100%, no derating | 30A (full rated) |
| 4–6 conductors | 80% | 24A |
| 7–9 conductors | 70% | 21A |
| 10–20 conductors | 50% | 15A |
| 21–30 conductors | 45% | 13.5A |
⚠️ Important: EGCs and neutrals carrying only unbalanced current do not count as current-carrying conductors for derating. They do count for fill. Keep the two calculations separate; they use different conductor counts.
Download the Free PDF: Print-Ready Conduit Fill Reference
Two-page landscape PDF covering EMT, PVC Schedule 40, and RMC from 14 AWG to 500 kcmil, plus conduit dimension reference and Canadian wire type equivalents. Print it, laminate it, keep it on site.
Frequently Asked Questions
Does Canada use NEC or CEC for conduit fill? ▾
Canada uses the CEC, not the NEC, but the fill percentages are identical in both: 53% for one conductor, 31% for two, 40% for three or more, and 60% for nipples under 600 mm. CEC Rule 12-910 governs this. The practical difference is wire naming: RW90 instead of THHN/THWN-2, TWN75 instead of THWN. The cross-sectional areas are the same, so every table on this page applies directly to Canadian installations.
How many 12 AWG wires fit in a 3/4″ EMT conduit? ▾
Sixteen conductors at 40% fill. A 3/4″ EMT has a total internal area of 0.533 in², and 40% of that is 0.213 in². Each 12 AWG THWN/RW90 conductor takes up 0.0133 in². Divide: 0.213 by 0.0133 to get 16. For exactly two conductors the 31% rule applies, bringing the limit to 12. For a single conductor at 53% fill the limit is 21.
What is the maximum fill percentage for conduit in Canada? ▾
CEC Rule 12-910 sets these limits: 53% for one conductor, 31% for two, 40% for three or more, and 60% for nipples 600 mm or shorter. On long runs with multiple bends, most installers aim for 30% or less regardless of the code maximum.
Does the ground wire count in conduit fill calculations? ▾
Yes. Every conductor in the conduit counts for fill, including the equipment ground. EGCs are excluded from ampacity derating but not from fill calculations. Two different rules, two different conductor counts.
Can I use the same conduit fill tables for RW90 and THWN? ▾
Yes. RW90 and THWN/THHN are different designations for conductors with the same cross-sectional areas. The CEC Tables 6A-6K match NEC Chapter 9 Table 5. Every value in these tables applies directly to RW90 installations.
What is the difference between EMT, PVC Schedule 40, and RMC for conduit fill? ▾
Same fill percentages, different internal diameters. PVC Schedule 40 is slightly larger than EMT of the same trade size, so it holds marginally more conductors. RMC has the thickest walls and smallest bore. EMT is the standard for commercial indoor work, PVC Sch 40 for underground runs, and RMC where the conduit needs to withstand physical abuse.
Why does conduit fill matter beyond code compliance? ▾
Three reasons beyond code compliance. First, heat: tightly packed conductors trap heat, degrading insulation and reducing ampacity over time. Second, pull tension: overfilled conduits with multiple bends require pull forces that can damage insulation during installation. Third, future work: a conduit filled to the maximum leaves no room for additions, which means a full new run the next time a circuit needs to change. Designing to 30 to 35% fill means you can absorb one future conductor without reworking anything.
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