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Voltage Drop Calculator

Price voltage drop for single- and three-phase runs.

Inputs

Run

Current the run must carry.

Distance from the source to the load, measured along the conductor, not the round trip.

Copper conductor. Circular mil values come from NEC Chapter 9 Table 8.

Circuit nominal voltage: 120, 240, 208, 480.

Conductor and limit

12.9 for copper, 21.2 for aluminum. K is the resistivity in ohm-circular-mils per foot at operating temperature.

NEC 210.19(A) informational note recommends 3% on a branch circuit and 5% total for reasonable efficiency of operation. It is not a mandatory rule in all editions; confirm the adopted edition and any local requirement.

Result

Meets the limit (1 = yes)
0
Drop, single phase
6.32 V
Drop, single phase
5.3 %
Voltage at the load
113.7 V
Maximum length at the limit
57 ft
Drop, three phase
5.47 V
Drop, three phase
4.6 %

What to check

  • Run length
  • Wire circular mils
  • K factor

Keep going

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Screening tool. Verify against the NEC as adopted locally, the AHJ, nameplate data, and metered conditions before acting.

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