Professional wire sizing tool optimized for the Canadian Electrical Code (CEC). Ensure Rule 8-102 compliance for your installations.
Unlike the US NEC, voltage drop limits in Canada are legally mandatory. Our calculator helps you navigate Rule 8-102 and Table D3 constants for professional certification.
The Canadian Electrical Code (CEC) is strict: feeders and branch circuits must not exceed a 3% voltage drop individually. When combined, the total drop from the service point to the furthest outlet must stay under 5%.
| Project Scope | CEC Limit | Requirement |
|---|---|---|
| Feeder Circuits | 3% Max | Mandatory |
| Branch Circuits | 3% Max | Mandatory |
| Total System | 5% Max | Mandatory |
Installations failing Rule 8-102 will fail inspection. This isn't a suggestion—it's federal law in Canada.
Canadian winters vs. summer peak loads require careful selection of 60°C, 75°C, or 90°C termination ratings.
We use accurate Ω/km values from the CEC Table D3 to ensure your voltage drop math matches the inspector's.
Long runs common in rural Canada make voltage drop the #1 factor in wire sizing over simple ampacity.
Maximum one-way meters allowed to stay under 3% CEC limit (Copper @ 75°C)
| Load (Amps) | #14 AWG | #12 AWG | #10 AWG | #8 AWG |
|---|---|---|---|---|
| 12A (80% Load) | 11.6m | 18.4m | 29.3m | 46.7m |
| 15A (Full Load) | 9.3m | 14.7m | 23.5m | 37.3m |
| 20A (Kitchen) | - | 11.1m | 17.6m | 28.0m |
To accurately calculate voltage drop in Canada, you must use the resistance values (Ω/km) defined in Appendix D, Table D3 of the Canadian Electrical Code. Do not use NEC Table 8 values, as they differ slightly and will lead to compliance failures.
| AWG Size | Metric Area (mm²) | Copper Resistance (Ω/km) | Aluminum Resistance (Ω/km) | Max Ampacity (75°C) |
|---|---|---|---|---|
| 14 AWG | 2.08 | 10.30 | 16.90 | 15A |
| 12 AWG | 3.31 | 6.51 | 10.70 | 20A |
| 10 AWG | 5.26 | 4.09 | 6.72 | 30A |
| 8 AWG | 8.37 | 2.57 | 4.23 | 45A / 35A (Al) |
| 6 AWG | 13.30 | 1.62 | 2.66 | 65A / 50A (Al) |
| 4 AWG | 21.20 | 1.02 | 1.67 | 85A / 65A (Al) |
| 2 AWG | 33.60 | 0.64 | 1.05 | 115A / 90A (Al) |
| 1/0 AWG | 53.50 | 0.40 | 0.66 | 150A / 120A (Al) |
| 2/0 AWG | 67.40 | 0.32 | 0.52 | 175A / 135A (Al) |
| 3/0 AWG | 85.00 | 0.25 | 0.42 | 200A / 155A (Al) |
| 4/0 AWG | 107.00 | 0.20 | 0.33 | 230A / 180A (Al) |
Canada experiences some of the most extreme temperature swings globally. Table D3 values are normalized at a 60°C conductor temperature. However, most modern installations use 75°C or 90°C (like RW90 wire) termination ratings.
Running conductors at higher temperatures increases their resistance, which increases voltage drop. Always calculate for the worst-case scenario at max operating temperature.
Electricians transitioning from the US to Canada often fail inspections because of voltage drop. Here is why:
Use the actual connected load. If unknown, CEC requires using 80% of the breaker rating (e.g., 12A for a 15A breaker).
Find the specific resistance (Ω/km) for your chosen AWG and material (Copper/Aluminum).
For Single Phase: Vd = (2 × K × I × L) / 1000. Use L in meters.
Divide Vd by system voltage. Ensure it is ≤ 3% for branch circuits, or ≤ 5% for total system.
The Setup: You are trenching power to a detached garage 35 meters away from the main house panel in Alberta. You are installing a 240V, 40A subpanel. You want to use Aluminum NMWU.
The Calculation:
Result: FAILS INSPECTION (Exceeds 3%).
Solution: Upsize to #6 AWG Aluminum (Vd = 2.48%).
The Setup: Supplying a 3-phase 600V RTU on a commercial warehouse in Ontario. The run is 110 meters. The load is 65A. You are using Copper RW90.
The Calculation:
Result: FAILS INSPECTION (Exceeds 3%).
Solution: Upsize to #4 AWG Copper (Vd = 2.10%). Note: The high 600V system allows incredibly long runs compared to US 480V systems.
No. While the physics are identical, the NEC formula often uses Circular Mils (CM) and a fixed constant (K=12.9). The Canadian Electrical Code requires using the precise resistance values (Ω/km) listed in Table D3 to ensure your math matches the local inspector's expectations perfectly.
Rule 8-102(3) caps total drop at 5%. You must calculate the feeder drop (max 3%) and add it to the branch circuit drop (max 3%). For example, if your feeder drops 2.5%, your branch circuit can only drop 2.5% (Total 5.0%), even though the branch limit is technically 3%.
Table D3 provides a "Distance to center of distribution for a 1% drop". To get the 3% max distance, you multiply the table value by 3. Also, ensure you are adjusting for temperature. Our calculator does all this complex multi-step math automatically.
Yes. For lighting circuits, the 3% rule is strictly enforced. However, Rule 8-102 does have an exception (Subrule 4) that allows a greater voltage drop if the voltage at the utilization equipment remains within the equipment's operating tolerance, but this requires special engineering sign-off.
Switch to our 3-Phase calculator for 600V industrial Canadian motor and feeder calculations.