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Wire Size by Amps × Distance

Minimum copper size at 240 V single-phase and a 3% drop. Click any cell for the full breakdown including 120 V, aluminum and other budgets.

Amps \ Distance50 ft100 ft150 ft200 ft300 ft500 ft
15 A14 AWG12 AWG10 AWG8 AWG8 AWG4 AWG
20 A14 AWG10 AWG8 AWG8 AWG6 AWG4 AWG
30 A10 AWG8 AWG8 AWG6 AWG4 AWG2 AWG
40 A8 AWG8 AWG6 AWG4 AWG3 AWG1 AWG
50 A8 AWG6 AWG4 AWG4 AWG2 AWG1/0 AWG
60 A6 AWG6 AWG4 AWG3 AWG2 AWG2/0 AWG

Feeder cluster — subpanels & services

FeederCopper (3%)Aluminum (3%)
100 A @ 100 ft3 AWG1 AWG
100 A @ 150 ft2 AWG1/0 AWG
100 A @ 200 ft1 AWG2/0 AWG
100 A @ 300 ft2/0 AWG4/0 AWG
100 A @ 400 ft3/0 AWG250 kcmil
200 A @ 100 ft3/0 AWG250 kcmil
200 A @ 150 ft3/0 AWG250 kcmil
200 A @ 200 ft3/0 AWG250 kcmil
200 A @ 300 ft250 kcmil400 kcmil

12 V marine & RV combos

12 V circuitCopper @ 3%Copper @ 10%
20 A @ 10 ft8 AWG12 AWG
20 A @ 20 ft4 AWG10 AWG
20 A @ 30 ft3 AWG8 AWG
30 A @ 10 ft6 AWG10 AWG
30 A @ 20 ft3 AWG8 AWG
30 A @ 30 ft2 AWG6 AWG
50 A @ 10 ft4 AWG8 AWG
50 A @ 20 ft1 AWG6 AWG
50 A @ 30 ft2/0 AWG4 AWG

For anything outside these matrices, the wire size solver covers 12 V DC through 600 V three-phase with any custom drop budget.

Built & maintained by Murugan Vellaichamy · Every calculation verified against NEC Chapter 9 Table 8 & Table 310.16 published values · Informational reference — not engineering advice