Voltage Drop Calculator

Wire and Cable Technical Help - Wire Sizing

Below you'll find a few helpers along the way to properly sizing your wire or cable. As we are primarilly marine focused we have added some tables regarding the amperages as suggested by the ABYC for the marine environment. These standards might be a bit more strict then those in the automotive environment however, they err on the side of caution and were developed with safety in mind.

The volatge drop calculator will allow you to find the percentage of voltage drop as well as the current delivered at the end of the wire run. In the boating world it is suggested:
3% max voltage drop for conductors providing power to panels and switchboards, navigation lighting, bilge blowers, main DC feeders, and any other circuit where voltage drop should be kept to a minimum
10% max voltage drop on conductors used for general lighting and other non-critical circuits

The ampacity (amperage) tables on the left side help to choose the correct size cable to handle the power load for which you are trying to find the correct wiring. There are individual tables for single conductor and multiple conductor runs as current carrying conductors which are bundled together will transfer heat to each other in effect reducing their safe current handling capabilities

 
Voltage Drop Calculator

Allowable Amperage of Current Carrying Conductors Carrying Conductors Under 50V

As suggested by the ABYC
Allowable Amperage of Single Conductors Rated 105C
Size CM Area Ampacity of Engine Space
AWG Sqmm

18

0.8

16

1

14

2

12

3

10

5

8

8

6

13

4

21

2

34

1

42

1/0

53

2/0

68

4/0

107

AWG SAE

1,600

1,537

2,600

2,336

4,100

3,702

6,500

5,833

10,500

9,343

16,800

14,810

26,600

24,538

42,000

37,360

66,500

62,450

83,690

77,790

105,600

98,980

133,100

125,100

211,600

205,500

Outside Inside

20

17

25

21

35

30

45

38

60

51

80

68

120

102

160

136

210

178

245

208

285

242

330

280

445

378


Allowable Amperage of Conductors When Multiple Conductors
are Bundled Together for Cables Rated 105C
Number of Conductors
  • 2 Cond
  • 3 Cond
  • 4-6 Cond
  • 7-24 Cond
AWG Sqmm Outside Inside

18

0.8

20

17.0

16

1

25

21.3

14

2

35

29.8

12

3

45

38.3

10

5

60

51.0

8

8

80

68.0

6

13

120

102.0

4

21

160

136.0

2

34

210

178.5

1

42

245

208.3

1/0

53

285

242.3

2/0

68

330

280.5

4/0

107

445

378.3

AWG Sqmm Outside Engine Space Inside Engine Space

18

0.8

14.0

11.9

16

1

17.5

14.9

14

2

24.5

20.8

12

3

31.5

26.8

10

5

42.0

35.7

8

8

56.0

47.6

6

13

84.0

71.4

4

21

112.0

95.2

2

34

147.0

125.0

1

42

171.5

145.8

1/0

53

199.5

169.6

2/0

68

231.0

196.4

4/0

107

311.5

264.8

AWG Sqmm Outside Engine Space Inside Engine Space

18

0.8

12.0

10.2

16

1

15.0

12.8

14

2

21.0

17.9

12

3

27.0

23.0

10

5

36.0

30.6

8

8

48.0

40.8

6

13

72.0

61.2

4

21

96.0

81.6

2

34

126.0

107.1

1

42

147.0

125

1/0

53

171.0

145.4

2/0

68

198.0

168.3

4/0

107

267.0

227.0

AWG Sqmm Outside Engine Space Inside Engine Space

18

0.8

10.0

8.5

16

1

12.5

10.6

14

2

17.5

14.9

12

3

22.5

19.1

10

5

30.0

25.5

8

8

40.0

34.0

6

13

60.0

51.0

4

21

80.0

68.0

2

34

105.0

89.3

1

42

122.5

104.1

1/0

53

142.5

121.1

2/0

68

165.0

140.3

4/0

107

222.5

189.1