Measurement Guide

AMPERAGE
COPPER ALUMINUM
SIZE (AWG
OR kcmil)
TW, UF-B,
NM-B (60°C)
RHH, THW,
THWN, XHHW,
SE (75°C)
RHH, THHN, THWN-2,
XHHW-2, RHW-2,
USE-2 (90°C)
(60°C)
THW, RHH,
THWN, XHHW,
SE (75°C)
THHN, THWN-2,
XHHW-2, RHW-2,
USE-2 (90°C)
14 15 15 15 – – –
12 20 20 20 – – –
10 30 30 30 – – –
8 40 50 55 35 40 45
6 55 65 75 40 50 55
4 70 85 95 55 65 75
3 85 100 110 65 75 85
2 95 11 5 130 75 90 10 0
1 110 130 145 85 10 0 11 5
1/0 125 150 170 10 0 120 135
2/0 145 175 195 11 5 135 150
3/0 165 200 225 130 155 175
4/0 195 230 260 150 180 205
250 215 255 290 170 205 230
300 240 285 320 195 230 260
350 260 310 350 210 250 280
400 280 335 380 225 270 305
500 320 380 430 260 310 350
600 350 420 475 285 340 385
– 385 460 520 315 375 425
750 400 475 535 320 385 435
– 410 490 555 330 395 445
– 435 520 585 355 425 480
1000 455 545 615 375 445 500
Note: Ampacities for insulated wires or cables rated 0-2000 volts and not more than three current carrying conductors
in raceway or cable or earth. Based on 30°C (86°F) ambient. Ampacity is based upon the National Electrical Code.
AMPERAGE ALLOWANCE FOR
3-WIRE SINGLE PHASE
DWELLING SERVICES
SERVICE
RATING
(AMPS)
COPPER
SIZE (AWG)
OR KCMIL
ALUMINUM
SIZE (AWG)
OR KCMIL
10 0 4 2
125 2 1/0
150 1 2/0
200 2/0 4/0
225 3/0 250
250 4/0 300
300 250 350
350 350 500
400 400 600
RECOMMENDED CIRCUIT LENGTHS FOR VOLTAGE DROP*
WIRE SIZE
(AWG)
RATING OF CIRCUIT BREAKER OR FUSE IN AMPERES
15 20 30 40 50 60 70 80 90 100
14 40
C 12 65 50
O 10 105 80 55
P 8 160 120 80 60 50*
P 6 260 195 130 10 0 80 60*
E 4 420 305 205 155 120 100 85 70*
R 2 665 500 330 250 200 165 140 125 110 95*
A 6 155 11 5 80 60 50
L 4 245 185 125 95 75 60
U 2 295 295 200 150 120 10 0 85 75 65
*For single conductors (THHN/THWN(-2), XHHW-2, etc.) only. This amperage not allowed for types NM-B and UF-B cable.
Recommended maximum circuit lengths in feet for voltage system of 120 volts. For 240-volt systems, circuit lengths
may be doubled. Note: Extremely long circuits can produce voltage losses whereby some electrical equipment may
not operate properly. Following these recommended values should provide reasonable efficiency of operation.