Voltage Drop Chart

Name: Voltage Drop Chart: maximum run distances at 3%
Creator: ElectricalToolbox
License: https://electricaltoolbox.com/terms

Maximum one-way run distance, in feet, that keeps voltage drop within the NEC 3% recommendation, by conductor size and load. Computed with the same method as our Voltage Drop Calculator (NEC Chapter 9; unity power factor, 75°C). Print it, or use the calculator for exact conditions.

120 V single-phase, copper

Max one-way distance (ft) at ≤3% drop. "-" means the load exceeds the conductor's 75°C ampacity (NEC Table 310.16); voltage drop is moot.

AWG/kcmil	15 A	20 A	30 A	40 A	50 A	100 A
14	38 ft	28 ft	-	-	-	-
12	60 ft	45 ft	-	-	-	-
10	96 ft	72 ft	48 ft	-	-	-
8	153 ft	115 ft	76 ft	57 ft	46 ft	-
6	244 ft	183 ft	122 ft	91 ft	73 ft	-
4	388 ft	291 ft	194 ft	145 ft	116 ft	-
3	489 ft	367 ft	244 ft	183 ft	146 ft	73 ft
2	631 ft	473 ft	315 ft	236 ft	189 ft	94 ft
1	799 ft	600 ft	399 ft	300 ft	240 ft	120 ft
1/0	1000 ft	750 ft	500 ft	375 ft	300 ft	150 ft
2/0	1200 ft	899 ft	600 ft	449 ft	359 ft	179 ft
3/0	1558 ft	1168 ft	779 ft	584 ft	467 ft	233 ft
4/0	1935 ft	1451 ft	967 ft	725 ft	580 ft	290 ft

240 V single-phase, copper

Max one-way distance (ft) at ≤3% drop. "-" means the load exceeds the conductor's 75°C ampacity (NEC Table 310.16); voltage drop is moot.

AWG/kcmil	15 A	20 A	30 A	40 A	50 A	100 A
14	76 ft	57 ft	-	-	-	-
12	121 ft	91 ft	-	-	-	-
10	193 ft	144 ft	96 ft	-	-	-
8	307 ft	230 ft	153 ft	115 ft	92 ft	-
6	488 ft	366 ft	244 ft	183 ft	146 ft	-
4	776 ft	582 ft	388 ft	291 ft	232 ft	-
3	978 ft	734 ft	489 ft	367 ft	293 ft	146 ft
2	1263 ft	947 ft	631 ft	473 ft	378 ft	189 ft
1	1599 ft	1200 ft	799 ft	600 ft	480 ft	240 ft
1/0	2000 ft	1500 ft	1000 ft	750 ft	600 ft	300 ft
2/0	2400 ft	1799 ft	1200 ft	899 ft	719 ft	359 ft
3/0	3116 ft	2337 ft	1558 ft	1168 ft	935 ft	467 ft
4/0	3870 ft	2903 ft	1935 ft	1451 ft	1161 ft	580 ft

240 V single-phase, aluminum

Max one-way distance (ft) at ≤3% drop. "-" means the load exceeds the conductor's 75°C ampacity (NEC Table 310.16); voltage drop is moot.

AWG/kcmil	15 A	20 A	30 A	40 A	50 A	100 A
12	73 ft	55 ft	-	-	-	-
10	117 ft	88 ft	58 ft	-	-	-
8	186 ft	140 ft	93 ft	70 ft	-	-
6	297 ft	222 ft	148 ft	111 ft	89 ft	-
4	472 ft	354 ft	236 ft	177 ft	141 ft	-
3	595 ft	446 ft	297 ft	223 ft	178 ft	-
2	750 ft	562 ft	375 ft	281 ft	224 ft	-
1	960 ft	719 ft	480 ft	359 ft	288 ft	144 ft
1/0	1200 ft	899 ft	600 ft	449 ft	359 ft	179 ft
2/0	1500 ft	1125 ft	750 ft	562 ft	449 ft	224 ft
3/0	1846 ft	1384 ft	923 ft	692 ft	553 ft	276 ft
4/0	2400 ft	1799 ft	1200 ft	899 ft	719 ft	359 ft

Method and NEC reference

Distances are derived from NEC 2020 Chapter 9 conductor data: the K-factor method below 2 AWG and Table 9 effective impedance at 2 AWG and larger, at unity power factor and the 75°C basis, single-phase (round-trip) circuits. The 3% figure is the branch-circuit recommendation in the informational notes to NEC 210.19(A)(1); with feeder and branch combined, the recommendation is 5% (multiply distances by 5/3 ≈ 1.67 for a 5% budget). Voltage drop percentages scale linearly: a 240 V circuit allows exactly twice the distance of a 120 V circuit at the same current.

Results are for reference only. Verify against the applicable adopted edition of the NEC and consult a licensed electrician for code compliance.

How to read this chart

Find your load current in the column headers, read down to your planned one-way distance, and use the first conductor size whose distance meets or exceeds yours. Example: a 20 A load run 120 ft one-way at 120 V; 12 AWG allows less than that, so move to 10 AWG. Distances assume the entire load at the end of the run; distributed loads (a string of receptacles) see less drop than the chart implies, so the chart errs conservative.

The chart cannot see your ambient temperature, conduit fill, or termination ratings; those affect ampacity, not voltage drop, and can require a larger conductor than the chart shows. The Wire Size Calculator checks both constraints together.

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Studying for the licensing exam? Our own NEC Code Quickstart works all twelve exam calculations start to finish, each with the code reference. Also in paperback.

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