Maximum Cable Length

How far each conductor size can run before the voltage drop reaches 3%, expressed as ampere-feet: divide by the load current to get the maximum one-way length.

Copper ampere-feet for 3% voltage drop, one-way length

Size	120 V 1φ	208 V 3φ	277 V 1φ	480 V 3φ
14 AWG	586	1,173	1,353	2,707
12 AWG	932	1,865	2,151	4,304
10 AWG	1,482	2,966	3,420	6,844
8 AWG	2,356	4,716	5,439	10,882
6 AWG	3,746	7,498	8,648	17,304
4 AWG	5,957	11,923	13,751	27,514
3 AWG	7,512	15,034	17,339	34,694
2 AWG	9,472	18,958	21,864	43,749
1 AWG	11,944	23,905	27,570	55,166
1/0 AWG	15,061	30,144	34,766	69,563
2/0 AWG	18,991	38,011	43,839	87,718
3/0 AWG	23,948	47,931	55,279	111k
4/0 AWG	30,198	60,440	69,706	139k
250 kcmil	35,678	71,408	82,356	165k
300 kcmil	42,813	85,690	98,827	198k
350 kcmil	49,949	99,971	115k	231k
400 kcmil	57,084	114k	132k	264k
500 kcmil	71,355	143k	165k	330k
600 kcmil	85,626	171k	198k	395k
700 kcmil	99,897	200k	231k	461k
750 kcmil	107k	214k	247k	494k
800 kcmil	114k	229k	264k	527k
900 kcmil	128k	257k	296k	593k
1000 kcmil	143k	286k	329k	659k

Aluminum ampere-feet for 3% voltage drop, one-way length

Size	120 V 1φ	208 V 3φ	277 V 1φ	480 V 3φ
12 AWG	566	1,133	1,306	2,614
10 AWG	900	1,801	2,077	4,156
8 AWG	1,431	2,864	3,303	6,608
6 AWG	2,275	4,553	5,251	10,508
4 AWG	3,617	7,240	8,350	16,708
3 AWG	4,561	9,130	10,529	21,068
2 AWG	5,752	11,512	13,277	26,567
1 AWG	7,253	14,517	16,742	33,500
1/0 AWG	9,146	18,305	21,111	42,243
2/0 AWG	11,533	23,082	26,621	53,267
3/0 AWG	14,542	29,106	33,569	67,168
4/0 AWG	18,338	36,702	42,329	84,698
250 kcmil	21,665	43,363	50,011	100k
300 kcmil	25,998	52,035	60,013	120k
350 kcmil	30,332	60,708	70,015	140k
400 kcmil	34,665	69,380	80,017	160k
500 kcmil	43,331	86,726	100k	200k
600 kcmil	51,997	104k	120k	240k
700 kcmil	60,663	121k	140k	280k
750 kcmil	64,996	130k	150k	300k
800 kcmil	69,329	139k	160k	320k
900 kcmil	77,995	156k	180k	360k
1000 kcmil	86,661	173k	200k	400k

Calculated by RokBench from standard conductor resistivity and temperature coefficients (100% IACS copper, 61% IACS aluminum). © RokBench.