This calculator helps you determine the wire size needed for a given ampacity (MCA). Enter the values below and click “Calculate” to see the recommended wire size as per the Canadian Electrical Code (2021 CEC), CSA C22.1:21. If you need to derate your MCA, we have a calculator for that here.
Wire Size Calculator

Wire Size Calculator

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Minimum Circuit Ampacity (MCA):

Recommended Wire Size:

Size \ Temp. 60 75 90 110
14 25 30 35 40
12 30 35 40 45
10 40 50 55 65
8 60 70 80 90
6 80 95 105 120
4 105 125 140 160
3 120 145 165 185
2 140 170 190 215
1 165 195 220 245
0 195 230 260 290
2/0 220 265 300 335
3/0 260 310 350 390
4/0 300 360 405 455
250 340 405 455 510
300 370 445 500 560
350 425 505 570 640
400 455 545 615 690
500 520 620 700 785
600 580 690 780 870
700 630 755 850 955
750 655 785 885 990
800 680 815 920 1030
900 730 870 980 1100
1000 785 935 1055 1180
1250 890 1065 1200 1345
1500 985 1175 1325 1485
1750 1070 1280 1445 1620
2000 1160 1385 1560 1750

Ampacity Input (MCA)

The ampacity used to calculate the wire size is referred to the minimum circuit ampacity (MCA) after applying a voltage drop calculation to it. In the CEC and the NEC the MCA = 1.25 * FLA, where the FLA should be obtained from the nameplate or the manufacturer. If not, you can refer to Tables 44 and 45 of the CEC, or 430-148 and 430-150 of the NEC for these values.

In both the CEC and the NEC, the MCA of multiple motors is equal to the 1.25 * (FLA of largest motor) plus other motors.

 

MCA = 1.25(FLA of largest motor) + FLA of smaller motor 1 + FLA of smaller motor 2…

Parallel Runs

By running wires in parallel, the total ampacity of the circuit is increased. This allows for the transmission of higher currents without exceeding the ampacity limits of a single wire. Additionally they allow for flexibility in using different wire sizes based on specific needs. This can be advantageous when dealing with varying current requirements or when working with available wire sizes.

Circuit ampacity of 540A, and Copper conductors rated for 75°C:

 

Recommended wire size of 1000 MCM

 

in practice this wire size is large, expensive, hard to handle, and uncommon

 

Instead let’s use a parallel run, so we will divide the ampacity in two (2) by introducing a second parallel circuit:

 

New circuit ampacity for 2 runs: 540A/2 = 270A: Recommended wire size = 300 MCM

 

1 run of 1000 MCM or 2 runs of 300 MCM will carry 540A safely

 

** This can be done for multiple runs, if you want to run 3 parallel runs, then divide the ampacity by 3 instead **

Motor Conductor

It’s important to remember that rule 28-106 of the CEC states that the conductors of a branch circuit supplying a motor must be sized so that the ampacity of the conductors are not less than 125% of the motor’s FLA. If the FLA of a motor is 18A, then first you need to calculate the Minimum Circuit Ampacity (MCA), MCA = 125% * FLA = 1.25*18A, MCA = 23A. Using the MCA of 23A as the circuit ampacity, you’ll find that the recommended wire size (copper, 75°C) is 12AWG, instead of 14AWG is you had used the FLA value of 18A instead.

 

It’s important to choose the right wire size to ensure the safety and reliability of the system. To determine the required wire size, you’ll need to consider the amount of current that will be flowing through the wire, the distance the wire needs to run, and the type of insulation and environment the wire will be exposed to.

 

Choosing the wrong wire size can result in overheating, voltage drops, and even fires or electrical shocks. That’s why it’s crucial to take the time to calculate the proper wire size for your specific application.

 

Don’t make the mistake of assuming that bigger is always better when it comes to wire size. Choosing an oversized wire can lead to wasted resources and increased costs, while undersized wire can be a major safety hazard.

 

Use a wire size calculator or consult the Canadian Electrical Code to determine the right wire size for your job. Don’t cut corners or take shortcuts when it comes to electrical safety – choose the right wire size and install it properly to ensure the safety and reliability of your electrical system.

 

Using a wire size calculator can simplify the process of determining the required wire size. However, it is important to always verify the results with the CEC guidelines and consult a qualified electrical engineer or electrician for any installation or wiring questions.

Don’t have the FLA? Click on the link below for a FLA calculator:
Calculator with FLA in display