120 Volt Voltage Drop Tables

120 volts is the standard household voltage in the United States for general-purpose receptacles and lighting. It is derived from a 240-volt service by using one hot conductor and the neutral. Most residential branch circuits operate at 120 volts, including bedroom outlets, kitchen countertop circuits, bathroom circuits, lighting circuits, and general-purpose receptacles throughout the home.

Understanding Voltage Drop at 120V

Voltage drop is the reduction in voltage between the source (panel) and the load (device) caused by the resistance of the conductors. At 120 volts, a 3% voltage drop equals 3.6 volts, meaning the voltage at the load would be 116.4 volts. The NEC recommends keeping voltage drop below 3% for branch circuits and below 5% for the combined feeder and branch circuit. While these are recommendations rather than mandatory requirements, they represent accepted engineering practice and are enforced by most electrical inspectors.

Branch circuits at 120V are limited to 15 or 20 amps for general lighting and receptacle loads per NEC 210.3. The 80% rule for continuous loads means a 20A circuit should carry no more than 16A continuously.

Common 120V circuits include: 15A lighting, 20A kitchen outlets, 20A bathroom GFCI, 20A laundry, 20A garage, 15A bedroom, 20A outdoor, 20A workshop, 30A RV (TT-30). Each of these applications has specific NEC requirements for wire sizing, overcurrent protection, and installation methods. The tables below provide voltage drop values for copper conductors at various distances and amperages, organized by wire gauge, so you can quickly determine whether a specific gauge is adequate for your installation.

Quick Reference: Maximum Distance by Gauge at 120V

The table below shows the maximum one-way distance for each copper wire gauge at common amperages to maintain a voltage drop of 3% or less at 120 volts (single phase). If your run distance exceeds these values, you must use a larger wire gauge.

Gauge	10A Max Dist	15A Max Dist	20A Max Dist	30A Max Dist
14 AWG	57 ft	38 ft	28 ft	19 ft
12 AWG	90 ft	60 ft	45 ft	30 ft
10 AWG	145 ft	96 ft	72 ft	48 ft
8 AWG	231 ft	154 ft	115 ft	77 ft
6 AWG	366 ft	244 ft	183 ft	122 ft
4 AWG	584 ft	389 ft	292 ft	194 ft
3 AWG	734 ft	489 ft	367 ft	244 ft
2 AWG	927 ft	618 ft	463 ft	309 ft
1 AWG	1168 ft	779 ft	584 ft	389 ft
1/0 AWG	1475 ft	983 ft	737 ft	491 ft
2/0 AWG	1861 ft	1240 ft	930 ft	620 ft
3/0 AWG	2349 ft	1566 ft	1174 ft	783 ft
4/0 AWG	2960 ft	1973 ft	1480 ft	986 ft
250 kcmil	3495 ft	2330 ft	1747 ft	1165 ft
300 kcmil	4195 ft	2797 ft	2097 ft	1398 ft
350 kcmil	4904 ft	3269 ft	2452 ft	1634 ft
400 kcmil	5607 ft	3738 ft	2803 ft	1869 ft
500 kcmil	6976 ft	4651 ft	3488 ft	2325 ft

14 AWG Voltage Drop at 120V

Voltage drop values for 14 AWG copper conductor (3.14 ohms/kft) at 120 volts, single phase. Ampacity at 75°C: 20A. Cells in red exceed the 3% NEC recommendation.

Distance	10A	15A	20A	30A
25 ft	1.6V 1.3%	2.4V 2.0%	3.1V 2.6%	4.7V 3.9%
50 ft	3.1V 2.6%	4.7V 3.9%	6.3V 5.2%	9.4V 7.8%
75 ft	4.7V 3.9%	7.1V 5.9%	9.4V 7.8%	14.1V 11.8%
100 ft	6.3V 5.2%	9.4V 7.8%	12.6V 10.5%	18.8V 15.7%
125 ft	7.8V 6.5%	11.8V 9.8%	15.7V 13.1%	23.6V 19.6%
150 ft	9.4V 7.8%	14.1V 11.8%	18.8V 15.7%	28.3V 23.6%
200 ft	12.6V 10.5%	18.8V 15.7%	25.1V 20.9%	37.7V 31.4%
250 ft	15.7V 13.1%	23.6V 19.6%	31.4V 26.2%	47.1V 39.3%
300 ft	18.8V 15.7%	28.3V 23.6%	37.7V 31.4%	56.5V 47.1%
400 ft	25.1V 20.9%	37.7V 31.4%	50.2V 41.9%	75.4V 62.8%
500 ft	31.4V 26.2%	47.1V 39.3%	62.8V 52.3%	94.2V 78.5%

12 AWG Voltage Drop at 120V

Voltage drop values for 12 AWG copper conductor (1.98 ohms/kft) at 120 volts, single phase. Ampacity at 75°C: 25A. Cells in red exceed the 3% NEC recommendation.

Distance	10A	15A	20A	30A
25 ft	1.0V 0.8%	1.5V 1.2%	2.0V 1.6%	3.0V 2.5%
50 ft	2.0V 1.6%	3.0V 2.5%	4.0V 3.3%	5.9V 5.0%
75 ft	3.0V 2.5%	4.5V 3.7%	5.9V 5.0%	8.9V 7.4%
100 ft	4.0V 3.3%	5.9V 5.0%	7.9V 6.6%	11.9V 9.9%
125 ft	5.0V 4.1%	7.4V 6.2%	9.9V 8.3%	14.8V 12.4%
150 ft	5.9V 5.0%	8.9V 7.4%	11.9V 9.9%	17.8V 14.8%
200 ft	7.9V 6.6%	11.9V 9.9%	15.8V 13.2%	23.8V 19.8%
250 ft	9.9V 8.3%	14.8V 12.4%	19.8V 16.5%	29.7V 24.8%
300 ft	11.9V 9.9%	17.8V 14.8%	23.8V 19.8%	35.6V 29.7%
400 ft	15.8V 13.2%	23.8V 19.8%	31.7V 26.4%	47.5V 39.6%
500 ft	19.8V 16.5%	29.7V 24.8%	39.6V 33.0%	59.4V 49.5%

10 AWG Voltage Drop at 120V

Voltage drop values for 10 AWG copper conductor (1.24 ohms/kft) at 120 volts, single phase. Ampacity at 75°C: 35A. Cells in red exceed the 3% NEC recommendation.

Distance	10A	15A	20A	30A
25 ft	0.6V 0.5%	0.9V 0.8%	1.2V 1.0%	1.9V 1.6%
50 ft	1.2V 1.0%	1.9V 1.6%	2.5V 2.1%	3.7V 3.1%
75 ft	1.9V 1.6%	2.8V 2.3%	3.7V 3.1%	5.6V 4.7%
100 ft	2.5V 2.1%	3.7V 3.1%	5.0V 4.1%	7.4V 6.2%
125 ft	3.1V 2.6%	4.7V 3.9%	6.2V 5.2%	9.3V 7.8%
150 ft	3.7V 3.1%	5.6V 4.7%	7.4V 6.2%	11.2V 9.3%
200 ft	5.0V 4.1%	7.4V 6.2%	9.9V 8.3%	14.9V 12.4%
250 ft	6.2V 5.2%	9.3V 7.8%	12.4V 10.3%	18.6V 15.5%
300 ft	7.4V 6.2%	11.2V 9.3%	14.9V 12.4%	22.3V 18.6%
400 ft	9.9V 8.3%	14.9V 12.4%	19.8V 16.5%	29.8V 24.8%
500 ft	12.4V 10.3%	18.6V 15.5%	24.8V 20.7%	37.2V 31.0%

8 AWG Voltage Drop at 120V

Voltage drop values for 8 AWG copper conductor (0.778 ohms/kft) at 120 volts, single phase. Ampacity at 75°C: 50A. Cells in red exceed the 3% NEC recommendation.

Distance	10A	15A	20A	30A
25 ft	0.4V 0.3%	0.6V 0.5%	0.8V 0.7%	1.2V 1.0%
50 ft	0.8V 0.7%	1.2V 1.0%	1.6V 1.3%	2.3V 1.9%
75 ft	1.2V 1.0%	1.8V 1.5%	2.3V 1.9%	3.5V 2.9%
100 ft	1.6V 1.3%	2.3V 1.9%	3.1V 2.6%	4.7V 3.9%
125 ft	1.9V 1.6%	2.9V 2.4%	3.9V 3.2%	5.8V 4.9%
150 ft	2.3V 1.9%	3.5V 2.9%	4.7V 3.9%	7.0V 5.8%
200 ft	3.1V 2.6%	4.7V 3.9%	6.2V 5.2%	9.3V 7.8%
250 ft	3.9V 3.2%	5.8V 4.9%	7.8V 6.5%	11.7V 9.7%
300 ft	4.7V 3.9%	7.0V 5.8%	9.3V 7.8%	14.0V 11.7%
400 ft	6.2V 5.2%	9.3V 7.8%	12.4V 10.4%	18.7V 15.6%
500 ft	7.8V 6.5%	11.7V 9.7%	15.6V 13.0%	23.3V 19.4%

6 AWG Voltage Drop at 120V

Voltage drop values for 6 AWG copper conductor (0.491 ohms/kft) at 120 volts, single phase. Ampacity at 75°C: 65A. Cells in red exceed the 3% NEC recommendation.

Distance	10A	15A	20A	30A
25 ft	0.3V 0.2%	0.4V 0.3%	0.5V 0.4%	0.7V 0.6%
50 ft	0.5V 0.4%	0.7V 0.6%	1.0V 0.8%	1.5V 1.2%
75 ft	0.7V 0.6%	1.1V 0.9%	1.5V 1.2%	2.2V 1.8%
100 ft	1.0V 0.8%	1.5V 1.2%	2.0V 1.6%	3.0V 2.5%
125 ft	1.2V 1.0%	1.8V 1.5%	2.5V 2.0%	3.7V 3.1%
150 ft	1.5V 1.2%	2.2V 1.8%	3.0V 2.5%	4.4V 3.7%
200 ft	2.0V 1.6%	3.0V 2.5%	3.9V 3.3%	5.9V 4.9%
250 ft	2.5V 2.0%	3.7V 3.1%	4.9V 4.1%	7.4V 6.1%
300 ft	3.0V 2.5%	4.4V 3.7%	5.9V 4.9%	8.8V 7.4%
400 ft	3.9V 3.3%	5.9V 4.9%	7.9V 6.5%	11.8V 9.8%
500 ft	4.9V 4.1%	7.4V 6.1%	9.8V 8.2%	14.7V 12.3%

4 AWG Voltage Drop at 120V

Voltage drop values for 4 AWG copper conductor (0.308 ohms/kft) at 120 volts, single phase. Ampacity at 75°C: 85A. Cells in red exceed the 3% NEC recommendation.

Distance	10A	15A	20A	30A
25 ft	0.1V 0.1%	0.2V 0.2%	0.3V 0.3%	0.5V 0.4%
50 ft	0.3V 0.3%	0.5V 0.4%	0.6V 0.5%	0.9V 0.8%
75 ft	0.5V 0.4%	0.7V 0.6%	0.9V 0.8%	1.4V 1.2%
100 ft	0.6V 0.5%	0.9V 0.8%	1.2V 1.0%	1.9V 1.5%
125 ft	0.8V 0.6%	1.2V 1.0%	1.5V 1.3%	2.3V 1.9%
150 ft	0.9V 0.8%	1.4V 1.2%	1.9V 1.5%	2.8V 2.3%
200 ft	1.2V 1.0%	1.9V 1.5%	2.5V 2.0%	3.7V 3.1%
250 ft	1.5V 1.3%	2.3V 1.9%	3.1V 2.6%	4.6V 3.9%
300 ft	1.9V 1.5%	2.8V 2.3%	3.7V 3.1%	5.5V 4.6%
400 ft	2.5V 2.0%	3.7V 3.1%	4.9V 4.1%	7.4V 6.2%
500 ft	3.1V 2.6%	4.6V 3.9%	6.2V 5.1%	9.2V 7.7%

3 AWG Voltage Drop at 120V

Voltage drop values for 3 AWG copper conductor (0.245 ohms/kft) at 120 volts, single phase. Ampacity at 75°C: 100A. Cells in red exceed the 3% NEC recommendation.

Distance	10A	15A	20A	30A
25 ft	0.1V 0.1%	0.2V 0.1%	0.3V 0.2%	0.4V 0.3%
50 ft	0.3V 0.2%	0.4V 0.3%	0.5V 0.4%	0.7V 0.6%
75 ft	0.4V 0.3%	0.6V 0.5%	0.7V 0.6%	1.1V 0.9%
100 ft	0.5V 0.4%	0.7V 0.6%	1.0V 0.8%	1.5V 1.2%
125 ft	0.6V 0.5%	0.9V 0.8%	1.2V 1.0%	1.8V 1.5%
150 ft	0.7V 0.6%	1.1V 0.9%	1.5V 1.2%	2.2V 1.8%
200 ft	1.0V 0.8%	1.5V 1.2%	2.0V 1.6%	2.9V 2.5%
250 ft	1.2V 1.0%	1.8V 1.5%	2.5V 2.0%	3.7V 3.1%
300 ft	1.5V 1.2%	2.2V 1.8%	2.9V 2.5%	4.4V 3.7%
400 ft	2.0V 1.6%	2.9V 2.5%	3.9V 3.3%	5.9V 4.9%
500 ft	2.5V 2.0%	3.7V 3.1%	4.9V 4.1%	7.3V 6.1%

2 AWG Voltage Drop at 120V

Voltage drop values for 2 AWG copper conductor (0.194 ohms/kft) at 120 volts, single phase. Ampacity at 75°C: 115A. Cells in red exceed the 3% NEC recommendation.

Distance	10A	15A	20A	30A
25 ft	0.1V 0.1%	0.1V 0.1%	0.2V 0.2%	0.3V 0.2%
50 ft	0.2V 0.2%	0.3V 0.2%	0.4V 0.3%	0.6V 0.5%
75 ft	0.3V 0.2%	0.4V 0.4%	0.6V 0.5%	0.9V 0.7%
100 ft	0.4V 0.3%	0.6V 0.5%	0.8V 0.7%	1.2V 1.0%
125 ft	0.5V 0.4%	0.7V 0.6%	1.0V 0.8%	1.5V 1.2%
150 ft	0.6V 0.5%	0.9V 0.7%	1.2V 1.0%	1.8V 1.5%
200 ft	0.8V 0.7%	1.2V 1.0%	1.6V 1.3%	2.3V 1.9%
250 ft	1.0V 0.8%	1.5V 1.2%	1.9V 1.6%	2.9V 2.4%
300 ft	1.2V 1.0%	1.8V 1.5%	2.3V 1.9%	3.5V 2.9%
400 ft	1.6V 1.3%	2.3V 1.9%	3.1V 2.6%	4.7V 3.9%
500 ft	1.9V 1.6%	2.9V 2.4%	3.9V 3.2%	5.8V 4.8%

1 AWG Voltage Drop at 120V

Voltage drop values for 1 AWG copper conductor (0.154 ohms/kft) at 120 volts, single phase. Ampacity at 75°C: 130A. Cells in red exceed the 3% NEC recommendation.

Distance	10A	15A	20A	30A
25 ft	0.1V 0.1%	0.1V 0.1%	0.1V 0.1%	0.2V 0.2%
50 ft	0.1V 0.1%	0.2V 0.2%	0.3V 0.3%	0.5V 0.4%
75 ft	0.2V 0.2%	0.3V 0.3%	0.5V 0.4%	0.7V 0.6%
100 ft	0.3V 0.3%	0.5V 0.4%	0.6V 0.5%	0.9V 0.8%
125 ft	0.4V 0.3%	0.6V 0.5%	0.8V 0.6%	1.2V 1.0%
150 ft	0.5V 0.4%	0.7V 0.6%	0.9V 0.8%	1.4V 1.2%
200 ft	0.6V 0.5%	0.9V 0.8%	1.2V 1.0%	1.9V 1.5%
250 ft	0.8V 0.6%	1.2V 1.0%	1.5V 1.3%	2.3V 1.9%
300 ft	0.9V 0.8%	1.4V 1.2%	1.9V 1.5%	2.8V 2.3%
400 ft	1.2V 1.0%	1.9V 1.5%	2.5V 2.0%	3.7V 3.1%
500 ft	1.5V 1.3%	2.3V 1.9%	3.1V 2.6%	4.6V 3.9%

1/0 AWG Voltage Drop at 120V

Voltage drop values for 1/0 AWG copper conductor (0.122 ohms/kft) at 120 volts, single phase. Ampacity at 75°C: 150A. Cells in red exceed the 3% NEC recommendation.

Distance	10A	15A	20A	30A
25 ft	0.1V 0.1%	0.1V 0.1%	0.1V 0.1%	0.2V 0.1%
50 ft	0.1V 0.1%	0.2V 0.1%	0.2V 0.2%	0.4V 0.3%
75 ft	0.2V 0.1%	0.3V 0.2%	0.4V 0.3%	0.6V 0.5%
100 ft	0.2V 0.2%	0.4V 0.3%	0.5V 0.4%	0.7V 0.6%
125 ft	0.3V 0.3%	0.5V 0.4%	0.6V 0.5%	0.9V 0.8%
150 ft	0.4V 0.3%	0.6V 0.5%	0.7V 0.6%	1.1V 0.9%
200 ft	0.5V 0.4%	0.7V 0.6%	1.0V 0.8%	1.5V 1.2%
250 ft	0.6V 0.5%	0.9V 0.8%	1.2V 1.0%	1.8V 1.5%
300 ft	0.7V 0.6%	1.1V 0.9%	1.5V 1.2%	2.2V 1.8%
400 ft	1.0V 0.8%	1.5V 1.2%	1.9V 1.6%	2.9V 2.4%
500 ft	1.2V 1.0%	1.8V 1.5%	2.4V 2.0%	3.7V 3.0%

Other Voltage Levels

View voltage drop tables for other standard voltages. Higher voltages result in lower percentage voltage drop for the same absolute voltage loss, which allows longer conductor runs without upsizing.

120 Volt

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