600 kcmil Voltage Drop — Max Run Length by Load
Voltage drop for 600 kcmil copper and aluminium: at 20 A on 120 V single phase the 3% limit is reached at about 4186 ft one-way. Full table by load, voltage and distance.
Quick answer
600 kcmil copper reaches 3% voltage drop at about 4186 ft one-way carrying 20 A on a 120 V single-phase circuit. At 100 ft the same load drops 0.09 V (0.07%), calculated as VD = 2 × K × I × L / cmil with K = 12.9 for copper and 600,000 circular mils.
3% limit @ 20 A, 120 V
4186ft
3% limit @ 20 A, 240 V
8372ft
Drop @ 100 ft, 20 A
0.09V
Ω / 1000 ft (Cu)
0.0173
Maximum one-way run length at 3% drop
Copper 600 kcmil. Aluminium distances are roughly 62% of these figures.
| Load | 120 V 1Ø | 240 V 1Ø | 208 V 3Ø | 480 V 3Ø |
|---|---|---|---|---|
| 5 A | 16,744 ft | 33,488 ft | 33,514 ft | 77,340 ft |
| 10 A | 8,372 ft | 16,744 ft | 16,757 ft | 38,670 ft |
| 15 A | 5,581 ft | 11,162 ft | 11,171 ft | 25,780 ft |
| 20 A | 4,186 ft | 8,372 ft | 8,378 ft | 19,335 ft |
| 25 A | 3,348 ft | 6,697 ft | 6,702 ft | 15,468 ft |
| 30 A | 2,790 ft | 5,581 ft | 5,585 ft | 12,890 ft |
| 40 A | 2,093 ft | 4,186 ft | 4,189 ft | 9,667 ft |
| 50 A | 1,674 ft | 3,348 ft | 3,351 ft | 7,734 ft |
| 60 A | 1,395 ft | 2,790 ft | 2,792 ft | 6,445 ft |
| 80 A | 1,046 ft | 2,093 ft | 2,094 ft | 4,833 ft |
| 100 A | 837 ft | 1,674 ft | 1,675 ft | 3,867 ft |
Source & method: Derived from VD = 2 × K × I × L / cmil (1.732 × K × I × L / cmil for three phase), solved for L at 3% of nominal voltage. Run your exact circuit.
Voltage drop by distance at common loads
| Distance | 10 A | 15 A | 20 A | 30 A |
|---|---|---|---|---|
| 25 ft | 0.01% | 0.01% | 0.02% | 0.03% |
| 50 ft | 0.02% | 0.03% | 0.04% | 0.05% |
| 75 ft | 0.03% | 0.04% | 0.05% | 0.08% |
| 100 ft | 0.04% | 0.05% | 0.07% | 0.11% |
| 150 ft | 0.05% | 0.08% | 0.11% | 0.16% |
| 200 ft | 0.07% | 0.11% | 0.14% | 0.22% |
| 300 ft | 0.11% | 0.16% | 0.22% | 0.32% |
Published standard — source: Voltage drop from the standard VD formula with trade K constants
Frequently asked
- How far can you run 600 kcmil wire?
- At 20 A on a 120 V single-phase circuit, 600 kcmil copper stays under 3% voltage drop for about 4186 ft one-way. At 240 V the same load reaches roughly 8372 ft, because allowable drop scales with system voltage.
- What is the voltage drop of 600 kcmil wire per 100 feet?
- About 0.09 V at 20 A on 120 V single phase, using VD = 2 × K × I × L / cmil with K = 12.9 for copper.
- Is 3% voltage drop a code requirement?
- It is a recommendation, not a mandatory limit, in most adopted codes: roughly 3% on the branch circuit and 5% total including the feeder. Some local amendments and specifications do make it enforceable, so check what applies to your job.
- Does aluminium change the 600 kcmil numbers?
- Yes. Aluminium uses K = 21.2 instead of 12.9, so drop is about 64% higher for the same size and run, and allowable distance falls by roughly the same proportion.
More on 600 kcmil
Related charts & calculators
- Voltage Drop CalculatorPercent drop, end voltage and minimum conductor for any run length.
- Conduit Fill CalculatorFill percentage and maximum conductor count for EMT, RMC, IMC and PVC.
- Breaker Size CalculatorOvercurrent device rating and minimum conductor from load current.
- Wire Ampacity CalculatorDerated ampacity for ambient temperature and bundled conductors.
- Box Fill CalculatorVolume allowances for conductors, clamps, devices and grounds per NEC 314.16.
- Ampacity ChartEstimated allowable ampacity by conductor size, material and insulation rating.