Calculate voltage drop for sizing conductors, using CEC Table D3 and NEC Table 9 resistance and reactance values. The CEC and NEC generally target a maximum 3% voltage drop on branch circuits.
Voltage drop is the loss of voltage as current pushes through the resistance and reactance of a conductor. The longer the run and the higher the current, the more voltage you lose before it reaches the load.
Under the CEC, the calculator uses the resistance-only method: voltage drop equals the topology multiplier (2 for single-phase, 1.732 for three-phase) times the conductor resistance per metre times the current times the one-way length. CEC Table D3 Note 1 excludes reactance for typical branch and feeder work. Under the NEC, the calculator adds reactance from Chapter 9 Table 9 and accounts for power factor and conduit type, which matters on longer feeders and larger conductors.
Take a 120 V single-phase branch circuit: a #12 copper conductor carrying 16 A over a 20 m one-way run. Using the CEC resistance method, the drop works out to about 3.33 V, or 2.78 percent. That is just under the 3 percent branch-circuit target, so #12 is acceptable here but there is little margin left. Add a few more metres or a couple more amps and you would step up to #10.
The CEC addresses voltage drop in Rule 8-102, which generally targets a maximum of 3 percent on a branch circuit and 5 percent overall from the supply to the point of use. The resistance basis comes from CEC Table D3. The NEC treats 3 percent branch and 5 percent total as a recommendation in informational notes to Article 210.19 and 215.2 rather than a hard rule, and provides impedance data in Chapter 9 Table 9. Always confirm the current edition and any provincial amendments with your authority having jurisdiction.
The CEC targets 3 percent on a branch circuit and 5 percent total from the supply point to the load. The NEC treats the same figures as a recommendation rather than a hard limit. Confirm the current edition with your authority having jurisdiction.
For typical branch and feeder work, no. CEC Table D3 Note 1 uses a resistance-only basis. The NEC method in Chapter 9 Table 9 includes reactance and is power-factor aware, which matters more on longer runs and larger conductors.
Increase the conductor size, reduce the length, raise the system voltage where possible, or split the load across more circuits. Going up one wire size is usually the simplest fix.
Enter the one-way length. The topology multiplier in the formula already accounts for the current travelling out and back on a single-phase circuit.
Yes. Select the conductor material and the calculator uses the correct resistance for copper or aluminum at the chosen size.