Wire size vs. Voltage drop

Voltage drop can be calculated

Using Ohms Law

E = R I

where

E = voltage drop (Volts)

R = electrical resistance (Ohms)

I = current (Amps)

Example – Voltage Drop

Voltage drop in a 100 ft power line:

2 x 100 ft

#10 copper

electrical resistance 1.02 Ohm/1000 ft

current 10 Amps

can be calculated as

E = 2 (0.00102 Ohm/foot) (100 ft) (10 Amps)

= 2.04 Volts

Max Wire Feet @ 120 Volts, 1 Phase, 2% Max Voltage Drop
Amps	Volt-Amps	#14	#12	#10	#8	#6
1	120	450	700	1100	1800	2800
5	600	90	140	225	360	575
10	1200	45	70	115	180	285
15	1800	30	47	75	120	190
20	2400	–	36	57	90	140
25	3000	–	–	45	72	115
30	3600	–	–	38	60	95
40	4800	–	–	–	45	72
50	6000	–	–	–	–	57
Amps	Volt-Amps	#4	#2	1/0	2/0	3/0
1	120	4500	7000	–	–	–
5	600	910	1400	2250	2800	–
10	1200	455	705	1100	1400	1800
15	1800	305	485	770	965	1200
20	2400	230	365	575	725	900
25	3000	180	290	460	580	720
30	3600	150	240	385	490	600
40	4800	115	175	290	360	440
50	6000	90	145	230	290	360
60	7200	76	120	190	240	305
70	8400	65	105	165	205	260
80	9600	–	90	144	180	230

Max Wire Feet @ 240 Volts, 1 Phase, 2% Max Voltage Drop
Amps	Volt-Amps	#14	#12	#10	#8	#6
1	240	900	1400	2200	3600	5600
5	1200	180	285	455	720	1020
10	2400	90	140	225	360	525
15	3600	60	95	150	240	350
20	4800	–	70	110	180	265
25	6000	–	–	90	144	210
30	7200	–	–	75	120	175
40	5600	–	–	–	90	130
50	12000	–	–	–	–	105
Amps	Volt-Amps	#4	#2	1/0	2/0	3/0
1	240	9000	–	–	–	–
5	1200	1750	2800	4500	5600	7000
10	2400	910	1400	2200	2800	3600
15	3600	605	965	1500	1900	2400
20	4800	455	725	1100	1400	1800
25	6000	365	580	920	1100	1440
30	7200	300	485	770	970	1200
40	5600	230	360	575	725	880
50	12000	180	290	460	580	720
60	14400	150	240	385	485	600
70	16800	130	205	330	415	520
80	19200	–	180	290	365	440
100	24000	–	–	230	280	360
150	36000	–	–	185	190	240
200	48000	–	–	–	–	180