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DC Wire Gauge and Voltage Drop Calculator: What Size Cable Do You Actually Need?

What cable gauge for this current over this run?

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1 · The circuitContinuous current, not surge

Circuit preset

Populates current, length and drop target. Every field stays editable.

Circuit side

PV side takes the percentage against array Vmp, not battery voltage.

Current A

Continuous draw, not surge. Surge sizing is T3’s job.

One-way run length ft

Source to load, one direction only. The tool doubles it for the return conductor.

System voltage V

Acceptable voltage drop %

3% is the default and it is not a conservative one.

Advanced tinned copper · 122°F · 105°C insulation · ≤3 bundled · not in an engine bay

Conductor material

Tinned is the default because it is what belongs in a vehicle.

Conductor temperature °F

Working temperature of the cable, not ambient air.

Insulation rating °C

Conductors bundled together

Engine bay or other high-ambient space

2 · Reference tableShown, not hidden

AWG	Circular mils	Ω/1000 ft @ 68°F	Ampacity (A)
18	1,624	6.64	20
16	2,583	4.18	25
14	4,107	2.62	35
12	6,530	1.65	45
10	10,380	1.04	60
8	16,510	0.646	80
6	26,240	0.404	120
4	41,740	0.253	160
2	66,360	0.16	210
1	83,690	0.127	245
1/0	105,600	0.1	285
2/0	133,100	0.0795	330
3/0	167,800	0.063	385
4/0	211,600	0.05	445

Stranded copper, uncoated, resistance at 68°F. Ampacity per ABYC E-11 for 105°C insulation outside engine spaces, three or fewer conductors bundled. Odd sizes (3, 5, 7 AWG) exist, are rarely stocked, and are excluded from the walk.

Source status: these figures are transcribed from the tool specification for build purposes and are not yet verified against the current published editions — NEC Chapter 9 Table 8 for conductor resistance and ABYC E-11 for ampacity and derates. Edition and last-checked date must be stated here before publication. A wire gauge tool carrying a stale ampacity column is worse than no tool.

Result

Minimum conductor

—AWG

At this gauge

Next size up

Ampacity check

Same circuit at a higher voltage

Show your working

This tool sizes conductors. It does not design an electrical system. It covers continuous current and voltage drop. It does not cover overcurrent protection placement, conductor routing, chafe and abrasion protection, termination method, or bonding and grounding — all of which determine whether an installation is safe, and none of which is a gauge number. Work you are not confident in should be checked by someone qualified.

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