How far can you run 14 AWG wire?

At 20 A on a 120 V single-phase circuit, 14 AWG copper stays under 3% voltage drop for about 28 ft one-way. At 240 V the same load reaches roughly 57 ft, because allowable drop scales with system voltage.

What is the voltage drop of 14 AWG wire per 100 feet?

About 12.56 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 14 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.

14 AWG Voltage Drop — Max Run Length by Load

Voltage drop for 14 AWG copper and aluminium: at 20 A on 120 V single phase the 3% limit is reached at about 28 ft one-way. Full table by load, voltage and distance.

Quick answer

14 AWG copper reaches 3% voltage drop at about 28 ft one-way carrying 20 A on a 120 V single-phase circuit. At 100 ft the same load drops 12.56 V (10.47%), calculated as VD = 2 × K × I × L / cmil with K = 12.9 for copper and 4,107 circular mils.

3% limit @ 20 A, 120 V

28ft

3% limit @ 20 A, 240 V

57ft

Drop @ 100 ft, 20 A

12.56V

Ω / 1000 ft (Cu)

2.5252

Maximum one-way run length at 3% drop

Copper 14 AWG. Aluminium distances are roughly 62% of these figures.

Load	120 V 1Ø	240 V 1Ø	208 V 3Ø	480 V 3Ø
5 A	114 ft	229 ft	229 ft	529 ft
10 A	57 ft	114 ft	114 ft	264 ft
15 A	38 ft	76 ft	76 ft	176 ft
20 A	28 ft	57 ft	57 ft	132 ft
25 A	22 ft	45 ft	45 ft	105 ft
30 A	19 ft	38 ft	38 ft	88 ft
40 A	14 ft	28 ft	28 ft	66 ft
50 A	11 ft	22 ft	22 ft	52 ft
60 A	9 ft	19 ft	19 ft	44 ft
80 A	7 ft	14 ft	14 ft	33 ft
100 A	5 ft	11 ft	11 ft	26 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	1.31%	1.96%	2.62%	3.93%
50 ft	2.62%	3.93%	5.23%	7.85%
75 ft	3.93%	5.89%	7.85%	11.78%
100 ft	5.23%	7.85%	10.47%	15.7%
150 ft	7.85%	11.78%	15.7%	23.56%
200 ft	10.47%	15.7%	20.94%	31.41%
300 ft	15.7%	23.56%	31.41%	47.11%

Percent drop, 120 V single phase, copper.

Published standard

Frequently asked

How far can you run 14 AWG wire?: At 20 A on a 120 V single-phase circuit, 14 AWG copper stays under 3% voltage drop for about 28 ft one-way. At 240 V the same load reaches roughly 57 ft, because allowable drop scales with system voltage.
What is the voltage drop of 14 AWG wire per 100 feet?: About 12.56 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 14 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.

14 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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