Wire Size Calculator Canada — CEC Guide Canadian Electrical Code 2026
Wire sizing in Canada follows the Canadian Electrical Code (CEC), which uses AWG sizing similar to the US NEC but with some key differences. Common sizes: 14 AWG for 15A, 12 AWG for 20A, 10 AWG for 30A, 8 AWG for 40A, 6 AWG for 50-55A. The CEC Table 2 provides ampacity ratings, and correction factors for temperature, grouping, and installation method must be applied.
CEC Table 2 — Wire Ampacity
CEC Table 2 provides ampacity for copper conductors (similar to NEC 310.16 but with Canadian-specific values). For NMD90 cable (Canadian Romex) at 90°C rating but limited by termination temperature: 14 AWG: 15A. 12 AWG: 20A. 10 AWG: 30A. 8 AWG: 40A. 6 AWG: 55A. 4 AWG: 70A. 3 AWG: 85A. 2 AWG: 95A. 1 AWG: 110A. 1/0: 125A. These values are for two conductors in a cable or raceway with a 30°C ambient temperature.
CEC vs NEC — Key Differences
While the CEC and NEC are similar, there are important differences: 1. CEC allows 90°C ampacity for NMD90 cable with appropriate terminations (NEC limits NM-B to 60°C column). 2. Different table numbers: CEC Table 2 vs NEC Table 310.16. 3. Canadian-specific cable types: NMD90 (vs NM-B), NMWU (underground), TECK cable for industrial. 4. CEC Rule 8-104 governs maximum conductor length based on voltage drop (not just an informational note as in NEC). 5. CEC uses °C for temperature ratings exclusively (not °F). 6. Metric conduit sizes are used alongside imperial in Canada.
Correction Factors
CEC requires applying correction factors to Table 2 values: Temperature (Table 5A): At 30°C ambient = 1.00 (base). At 35°C = 0.96. At 40°C = 0.91. At 45°C = 0.87. These are important for attic runs and industrial environments. Grouping (Table 5C): 1-3 conductors = 1.00. 4-6 = 0.80. 7-24 = 0.70. 25-42 = 0.60. Applies when multiple cables are bundled or in the same raceway. CEC Rule 4-004(1): Derated ampacity = Table 2 value × temperature factor × grouping factor.
Common Canadian Circuits
15A general purpose: 14 AWG NMD90 on 15A breaker. Lighting and general receptacles. Maximum 12 outlets per circuit (CEC Rule 8-304(1)). 20A kitchen/bathroom: 12 AWG NMD90 on 20A breaker. CEC requires dedicated circuits for kitchen countertop and bathroom. 30A dryer: 10 AWG on 30A breaker with NEMA 14-30 receptacle. 40A range: 8 AWG on 40A breaker with NEMA 14-50 receptacle (CEC allows 40A for most ranges). 50A EV charger: 6 AWG on 50A breaker (40A continuous × 1.25 = 50A per CEC continuous load rule).
| AWG | Ampacity (90°C) | Typical Breaker | Common Use |
|---|---|---|---|
| 14 | 15A | 15A | Lighting, general outlets |
| 12 | 20A | 20A | Kitchen, bathroom, outdoor |
| 10 | 30A | 30A | Dryer, small AC |
| 8 | 40A | 40A | Range, hot tub |
| 6 | 55A | 50A | EV charger, sub-panel feed |
| 4 | 70A | 70A | Sub-panel feed |
| 2 | 95A | 90-100A | Large sub-panel |
| 1/0 | 125A | 125A | Sub-panel, service |
Voltage Drop — CEC Rule 8-102
CEC Rule 8-102 limits voltage drop to 5% total from service entrance to the farthest outlet. This is a code requirement in Canada, not just a recommendation (unlike the NEC informational note). For branch circuits, keeping VD under 3% is best practice, with 2% left for the feeder. The formula is the same as NEC: VD = (2 × L × I × R) / CMA. For a 20A circuit on 12 AWG at 30m: VD = (2 × 30 × 20 × 10.37) / 6530 ÷ 120 × 100 = 1.6%. Use our Voltage Drop Calculator — it works for both CEC and NEC.
Disclaimer: For educational reference only. Consult a licensed professional.