How far can you run 10 AWG wire?

At 20 A on a 120 V single-phase circuit, 10 AWG copper stays under 3% voltage drop for about 72 ft one-way. At 240 V the same load reaches roughly 144 ft, because allowable drop scales with system voltage.

What is the voltage drop of 10 AWG wire per 100 feet?

About 4.97 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 10 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.

10 AWG Voltage Drop — Max Run Length by Load

Voltage drop for 10 AWG copper and aluminium: at 20 A on 120 V single phase the 3% limit is reached at about 72 ft one-way. Full table by load, voltage and distance.

Quick answer

10 AWG copper reaches 3% voltage drop at about 72 ft one-way carrying 20 A on a 120 V single-phase circuit. At 100 ft the same load drops 4.97 V (4.14%), calculated as VD = 2 × K × I × L / cmil with K = 12.9 for copper and 10,383 circular mils.

3% limit @ 20 A, 120 V

72ft

3% limit @ 20 A, 240 V

144ft

Drop @ 100 ft, 20 A

4.97V

Ω / 1000 ft (Cu)

0.9988

Maximum one-way run length at 3% drop

Copper 10 AWG. Aluminium distances are roughly 62% of these figures.

Load	120 V 1Ø	240 V 1Ø	208 V 3Ø	480 V 3Ø
5 A	289 ft	579 ft	579 ft	1,338 ft
10 A	144 ft	289 ft	289 ft	669 ft
15 A	96 ft	193 ft	193 ft	446 ft
20 A	72 ft	144 ft	144 ft	334 ft
25 A	57 ft	115 ft	115 ft	267 ft
30 A	48 ft	96 ft	96 ft	223 ft
40 A	36 ft	72 ft	72 ft	167 ft
50 A	28 ft	57 ft	57 ft	133 ft
60 A	24 ft	48 ft	48 ft	111 ft
80 A	18 ft	36 ft	36 ft	83 ft
100 A	14 ft	28 ft	28 ft	66 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	0.52%	0.78%	1.04%	1.55%
50 ft	1.04%	1.55%	2.07%	3.11%
75 ft	1.55%	2.33%	3.11%	4.66%
100 ft	2.07%	3.11%	4.14%	6.21%
150 ft	3.11%	4.66%	6.21%	9.32%
200 ft	4.14%	6.21%	8.28%	12.42%
300 ft	6.21%	9.32%	12.42%	18.64%

Percent drop, 120 V single phase, copper.

Published standard

Frequently asked

How far can you run 10 AWG wire?: At 20 A on a 120 V single-phase circuit, 10 AWG copper stays under 3% voltage drop for about 72 ft one-way. At 240 V the same load reaches roughly 144 ft, because allowable drop scales with system voltage.
What is the voltage drop of 10 AWG wire per 100 feet?: About 4.97 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 10 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.

10 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

More on 10 AWG

Related charts & calculators