ROP VOLTAGE

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Voltage drop is one of those things that doesn’t matter—until it really does. Long runs, high loads, and undersized conductors can leave you with low voltage at the far end of the circuit, nuisance tripping, poor equipment performance, or even code issues. This Voltage Drop Calculator gives you a fast way to check how a proposed circuit will behave before you pull a single wire. It factors in system type (single-phase or three-phase), actual load, run length, conductor material, size, and even operating temperature to estimate real-world voltage drop and ending voltage at the load.

Because it works from basic physics (resistivity, cross-sectional area, and temperature correction), this tool is useful for everything from quick field checks to early design decisions. You can compare copper vs aluminum, different AWG or kcmil sizes, or metric cable, and instantly see how those choices change the voltage drop and percentage loss. That makes it an excellent companion when you’re trying to balance cost, conductor size, and performance while staying within common NEC/CEC recommendations (like 3% branch circuit and 5% feeder drop).

Start by selecting the system type (single-phase or three-phase) and entering the supply voltage. Next, choose how you want to enter the load:

• Current (A) – if you already know the load current, just enter it directly.
   
• Power (W) + PF – if you know the wattage and power factor, the calculator will work out the current for you, using the correct single-phase or three-phase formula.
   

Then, set up the run details: enter the one-way length of the circuit and choose feet or metres (the tool automatically accounts for the return path on single-phase circuits). Select conductor material (copper or aluminum), then choose your size mode: either pick a standard AWG/kcmil size from the list, or enter a custom mm² area for metric cable. Finally, set the operating temperature of the conductor – the calculator adjusts resistivity from 20 °C using typical temperature coefficients for copper and aluminum.

Once those fields are filled in, the results update to show:

• The current used in the calculation
   
• The resistance per metre of one conductor
   
• The voltage drop (V) across the run
   
• The percent voltage drop relative to supply
   
• The ending voltage at the load
   

Because the tool is interactive, you can quickly experiment: bump the wire size up or down, swap copper for aluminum, change the run length, or adjust the load and see the effect in real time. Use it as a quick design check, a teaching aid for apprentices, or a way to justify conductor sizing decisions to clients and inspectors—while remembering that it’s a simplified, resistance-only model and that final designs must still meet all applicable NEC/CEC requirements and manufacturer recommendations.