How far can you run 6 AWG wire?

At 20 A on a 120 V single-phase circuit, 6 AWG copper stays under 3% voltage drop for about 183 ft one-way. At 240 V the same load reaches roughly 366 ft, because allowable drop scales with system voltage.

What is the voltage drop of 6 AWG wire per 100 feet?

About 1.97 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 6 AWG 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.

6 AWG Voltage Drop — Max Run Length by Load

Voltage drop for 6 AWG copper and aluminium: at 20 A on 120 V single phase the 3% limit is reached at about 183 ft one-way. Full table by load, voltage and distance.

Quick answer

6 AWG copper reaches 3% voltage drop at about 183 ft one-way carrying 20 A on a 120 V single-phase circuit. At 100 ft the same load drops 1.97 V (1.64%), calculated as VD = 2 × K × I × L / cmil with K = 12.9 for copper and 26,251 circular mils.

3% limit @ 20 A, 120 V

183ft

3% limit @ 20 A, 240 V

366ft

Drop @ 100 ft, 20 A

1.97V

Ω / 1000 ft (Cu)

0.3951

Maximum one-way run length at 3% drop

Copper 6 AWG. Aluminium distances are roughly 62% of these figures.

Load	120 V 1Ø	240 V 1Ø	208 V 3Ø	480 V 3Ø
5 A	732 ft	1,465 ft	1,466 ft	3,383 ft
10 A	366 ft	732 ft	733 ft	1,691 ft
15 A	244 ft	488 ft	488 ft	1,127 ft
20 A	183 ft	366 ft	366 ft	845 ft
25 A	146 ft	293 ft	293 ft	676 ft
30 A	122 ft	244 ft	244 ft	563 ft
40 A	91 ft	183 ft	183 ft	422 ft
50 A	73 ft	146 ft	146 ft	338 ft
60 A	61 ft	122 ft	122 ft	281 ft
80 A	45 ft	91 ft	91 ft	211 ft
100 A	36 ft	73 ft	73 ft	169 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	0.2%	0.31%	0.41%	0.61%
50 ft	0.41%	0.61%	0.82%	1.23%
75 ft	0.61%	0.92%	1.23%	1.84%
100 ft	0.82%	1.23%	1.64%	2.46%
150 ft	1.23%	1.84%	2.46%	3.69%
200 ft	1.64%	2.46%	3.28%	4.91%
300 ft	2.46%	3.69%	4.91%	7.37%

Percent drop, 120 V single phase, copper.

Published standard

Frequently asked

How far can you run 6 AWG wire?: At 20 A on a 120 V single-phase circuit, 6 AWG copper stays under 3% voltage drop for about 183 ft one-way. At 240 V the same load reaches roughly 366 ft, because allowable drop scales with system voltage.
What is the voltage drop of 6 AWG wire per 100 feet?: About 1.97 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 6 AWG 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.

6 AWG Voltage Drop — Max Run Length by Load

Maximum one-way run length at 3% drop

Voltage drop by distance at common loads

Frequently asked

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