Wire Size Calculator Canada (CEC Table 2 & 8-102)

Wire Size Calculator (Canada, CEC)

Size copper or aluminum conductors for Canadian installations. The calculator checks CEC Table 2 or Table 4 ampacity, the Rule 14-104 small-conductor limits and the Rule 8-102 voltage drop limit, with lengths in metres or feet.

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.

How this calculator sizes a conductor

A conductor has to pass two separate checks, and the larger size wins:

Ampacity. The calculator takes the load (×125% if you mark it continuous, the same as keeping the calculated load at 80% of a standard-rated breaker), then finds the smallest size in CEC Table 2 (copper) or Table 4 (aluminum) whose ampacity in the chosen temperature column covers it. It also applies the Rule 14-104 small-conductor limits: 15 A for 14 AWG, 20 A for 12 AWG and 30 A for 10 AWG copper.
Voltage drop. Using the load current and the conductor resistance, it finds the smallest size that keeps the drop at or under your limit. CEC Rule 8-102 sets 3% for a feeder or branch circuit and 5% overall.

Short runs are usually decided by ampacity. Long runs, like a detached garage, a shop or a well pump, are usually decided by voltage drop. The result says which check controlled the size.

Formulas

Required ampacity = load × 1.25 (continuous) or load × 1.00
VD = k × I × R × L ÷ 1000, k = 2 (single phase) or 1.732 (three phase)
L in feet = L in metres × 3.28084

Worked examples

1. 30 A load to a detached garage, 240 V

At 30 m one way, 10 AWG copper passes ampacity (30 A limit under Rule 14-104) and drops 2 × 30 × 1.21 × 98.4 ÷ 1000 = 7.15 V, or 2.98% of 240 V. It just fits. Move the garage to 35 m and 10 AWG reaches 3.47%, so the answer becomes 8 AWG copper at 2.19%.

2. 15 A receptacle circuit at 120 V, 25 m

Ampacity allows 14 AWG copper, but the drop on 14 AWG is 6.29% and on 12 AWG still 3.96%. 10 AWG copper brings it to 2.48%. Long 120 V runs are where Rule 8-102 bites hardest, which is why many electricians move these loads to a subpanel.

3. 100 A subpanel feeder, aluminum, 240 V, 45 m

With 75 °C terminations, 1 AWG aluminum is rated 100 A in Table 4, so it passes ampacity. Over 45 m it drops 3.11%, just over the 3% feeder limit. One size up, 1/0 aluminum, drops 2.47%. In copper the same feeder needs 2 AWG (2.39%).

Choosing the temperature column

CEC Rule 4-006 limits the ampacity you can use to the temperature rating of the terminations the conductor lands on. Check the marking on the breaker, panel and equipment lugs before you use the 75 °C column. The 90 °C rating of RW90 or T90 conductors is mainly a starting point when you apply correction factors, not the final ampacity.

What this calculator does not cover

It does not apply correction factors for more than three conductors or high ambient temperature, the free-air ratings of Table 1, motor rules in Section 28, or bonding conductor sizing (Table 16). Use it to get the starting size, then confirm against the code edition adopted in your province and the inspector's requirements. To size the raceway for the result, use the Canadian conduit fill calculator.

Working to the NEC instead? Use the US wire size calculator.

Frequently asked questions

What size wire for a 30 amp circuit in Canada?

10 AWG copper is the usual minimum: CEC Rule 14-104 limits 10 AWG copper to 30 A overcurrent protection. On long runs the Rule 8-102 voltage drop limit can push you to 8 AWG. At 240 V and a 30 A load, 10 AWG copper reaches the 3% limit at about 30 m one way.

Are CEC Table 2 ampacities the same as NEC 310.16?

For copper conductors in raceway or cable (1 to 3 conductors, 30 °C ambient), the 60, 75 and 90 °C columns of CEC Table 2 match NEC Table 310.16 for 14 AWG through 1000 kcmil. Aluminum in Table 4 matches 310.16 for the common sizes. See the CEC Table 2 chart for the full comparison.

What load current should I use for voltage drop in Canada?

Rule 8-102 bases the voltage drop calculation on the connected load of the circuit if it is known, otherwise on 80% of the rating of the overcurrent device. If you do not know the load, enter 80% of the breaker size.

Is the 3% voltage drop limit mandatory in Canada?

Yes. Unlike the informational notes in the NEC, CEC Rule 8-102 is a requirement: 3% in a feeder or branch circuit and 5% total from the supply side of the consumer's service to the point of utilization.

Can I enter the run length in metres?

Yes. Choose m beside the length field. The calculator converts to feet (1 m = 3.28084 ft) and uses the same conductor resistance values.

Does the calculator apply correction factors?

No. Results assume 1 to 3 current-carrying conductors at a 30 °C ambient. Apply the CEC correction factors for more conductors or higher ambient temperatures, and check the termination temperature rating under Rule 4-006.