Voltage Drop Calculator
Calculate voltage drop for copper or aluminum wire runs. Check if your wire size passes the 3% guideline.
Frequently asked questions
- What is the 3% guideline?
- The NEC recommends keeping voltage drop under 3% on branch circuits and 5% total, so equipment sees close to its rated voltage.
- Why does the distance count twice?
- Current travels out on one conductor and returns on the other, so the total loop length is twice the one-way distance.
- When is aluminum acceptable?
- At larger sizes (typically 2 AWG and up) aluminum is common and economical. Below that, copper is preferred for terminations.
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