Temperature difference (wire rating minus the ambient °C) 4 5 6 7 8 9 10 20 30 40 50 60 70 80 90 100 300 200 100 90 80 70 60 50 40 30 1 Wire size 26 24 22 20 18 16 14 12 10 1 Temperature difference (wire rating minus the ambient °C) 40 50 60 70 80 90 100 200 300 400 500 600 700 800 900 1000 300 200 100 90 80 70 60 50 40 30 Current Amperes Wire size 8 6 4 1 1/0 2/0 3/0 4/0 2 NOT TO BE USED  AS SINGLE WIRE 1 9-73 Figure 9-117.  Single copper wire in free air.