How far can you run 16 AWG wire?

At 20 A on a 120 V single-phase circuit, 16 AWG copper stays under 3% voltage drop for about 18 ft one-way. At 240 V the same load reaches roughly 36 ft, because allowable drop scales with system voltage.

What is the voltage drop of 16 AWG wire per 100 feet?

About 19.98 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 16 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.

16 AWG Voltage Drop — Max Run Length by Load

Voltage drop for 16 AWG copper and aluminium: at 20 A on 120 V single phase the 3% limit is reached at about 18 ft one-way. Full table by load, voltage and distance.

Quick answer

16 AWG copper reaches 3% voltage drop at about 18 ft one-way carrying 20 A on a 120 V single-phase circuit. At 100 ft the same load drops 19.98 V (16.65%), calculated as VD = 2 × K × I × L / cmil with K = 12.9 for copper and 2,583 circular mils.

3% limit @ 20 A, 120 V

18ft

3% limit @ 20 A, 240 V

36ft

Drop @ 100 ft, 20 A

19.98V

Ω / 1000 ft (Cu)

4.0151

Maximum one-way run length at 3% drop

Copper 16 AWG. Aluminium distances are roughly 62% of these figures.

Load	120 V 1Ø	240 V 1Ø	208 V 3Ø	480 V 3Ø
5 A	72 ft	144 ft	144 ft	332 ft
10 A	36 ft	72 ft	72 ft	166 ft
15 A	24 ft	48 ft	48 ft	110 ft
20 A	18 ft	36 ft	36 ft	83 ft
25 A	14 ft	28 ft	28 ft	66 ft
30 A	12 ft	24 ft	24 ft	55 ft
40 A	9 ft	18 ft	18 ft	41 ft
50 A	7 ft	14 ft	14 ft	33 ft
60 A	6 ft	12 ft	12 ft	27 ft
80 A	4 ft	9 ft	9 ft	20 ft
100 A	3 ft	7 ft	7 ft	16 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	2.08%	3.12%	4.16%	6.24%
50 ft	4.16%	6.24%	8.32%	12.49%
75 ft	6.24%	9.36%	12.49%	18.73%
100 ft	8.32%	12.49%	16.65%	24.97%
150 ft	12.49%	18.73%	24.97%	37.46%
200 ft	16.65%	24.97%	33.29%	49.94%
300 ft	24.97%	37.46%	49.94%	74.91%

Percent drop, 120 V single phase, copper.

Published standard

Frequently asked

How far can you run 16 AWG wire?: At 20 A on a 120 V single-phase circuit, 16 AWG copper stays under 3% voltage drop for about 18 ft one-way. At 240 V the same load reaches roughly 36 ft, because allowable drop scales with system voltage.
What is the voltage drop of 16 AWG wire per 100 feet?: About 19.98 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 16 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.

16 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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