125A Feeder Wire Size at 60 Feet
A 125 A feeder at 60 ft sits between a 100 A subpanel and a 150 A feeder. The page uses the 5 percent feeder planning limit.
Formula SSC-2026.1
K method · SSC-2026.1
Minimum size
1 AWG · 42.4 mm²
Single conductor set
Voltage drop
2.31 V
0.96% · end 237.7 V
Power loss
289 W
I²R at the operating current
Required ampacity
125.0 A
Each conductor 130 A
Material estimate
$1,171.80
3 conductors + EMT
Conductor weight
54.0 lb
24.5 kg · approximate insulated weight
Circle diameters track circular mils. The drawing is a schematic, not a conduit-fill layout.
| Item | Net | Waste | Order | Unit price | Line total |
|---|---|---|---|---|---|
| copper 1 AWG · 42.4 mm² | 60 ft one way | cuts excluded | 3 conductors | USD | $1,060.80 |
| EMT conduit | 60 ft | — | 60 ft | USD | $111.00 |
| Material | Minimum size | mm² | Drop | End voltage | Loss |
|---|---|---|---|---|---|
| copper | 1 AWG · 42.4 mm² | 42.4 | 0.96% | 237.7 V | 289 W |
| aluminum | 2/0 AWG · 67.4 mm² | 67.4 | 1.00% | 237.6 V | 299 W |
| Distance | Minimum size | Drop | Percent | End voltage |
|---|---|---|---|---|
| 35 ft | 1 AWG · 42.4 mm² | 1.35 V | 0.56% | 238.7 V |
| 60 ft | 1 AWG · 42.4 mm² | 2.31 V | 0.96% | 237.7 V |
| 85 ft | 1 AWG · 42.4 mm² | 3.28 V | 1.36% | 236.7 V |
Show the deterministic formula
Single phase: Vdrop = 2 × K × I × D / cmil. Three phase: Vdrop = 1.732 × K × I × D / cmil. K is 12.9 for copper and 21.2 for aluminum. D is one-way feet.
Percent drop = Vdrop ÷ source voltage × 100. Green is 3% or less, amber is 3 to 5%, and red is over 5%. Power loss is I²R on the current-carrying conductors.
The smallest conductor that meets both the ampacity (125% when continuous) and the drop limit is selected. Ampacity does not include bundling or temperature correction.
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Project: 125A Feeder Wire Size at 60 Feet
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This sheet is an estimate for ordering and layout discussion. It is not a sealed design. Confirm the quantities with a licensed local professional and the authority having jurisdiction before you buy or build.
Engineering notes
A 125 A feeder at 60 ft sits between a 100 A subpanel and a 150 A feeder. The page uses the 5 percent feeder planning limit. The run is 60 ft one way at 125 A on 1ph-240. K is 12.9 for copper and 21.2 for aluminum. Ambient temperature, bundling, and rooftop adders are not applied.
Code reference
NEC 210.19(A) and 215.2(A) informational notes recommend 3 percent on a branch circuit and 5 percent total with the feeder. Ampacity follows the 75°C column of Table 310.16 plus the small-conductor limits. Confirm the adopted edition.
Field questions
- What current is used for the 125 A voltage drop?
- Both the drop and the ampacity check use the entered amps, because this preset is not marked continuous.
- Does this replace the equipment installation manual?
- No. The nameplate, the breaker, and the adopted NEC edition still control. This page is the K-method size and the percent drop.
- Can I switch copper and aluminum?
- Yes. The conductor control and the comparison table both recompute size, drop, and the planning cost.
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