Reference chart
Wire gauge and fuse chart for 12 V and 24 V
Updated October 22, 2026. Prices checked on the makers' own sites that day.
How to read it
Amps are the continuous current of the device on that cable (watts divided by volts). Length is one way, battery or bus bar to device. Gauges are AWG, copper, 105°C insulation. "1/0" and up are written as such.
12 V chart
| Amps | Fuse | 3 ft | 5 ft | 10 ft | 15 ft | 20 ft | 25 ft |
|---|---|---|---|---|---|---|---|
| 5 A | 7.5 A | 14 | 14 | 14 | 12 | 12 | 10 |
| 10 A | 15 A | 14 | 14 | 12 | 10 | 8 | 8 |
| 15 A | 20 A | 14 | 12 | 10 | 8 | 6 | 6 |
| 20 A | 25 A | 14 | 12 | 8 | 6 | 6 | 4 |
| 30 A | 40 A | 10 | 10 | 6 | 4 | 4 | 2 |
| 40 A | 50 A | 8 | 8 | 6 | 4 | 2 | 2 |
| 50 A | 70 A | 6 | 6 | 4 | 2 | 2 | 1 |
| 60 A | 80 A | 6 | 6 | 4 | 2 | 1 | 1/0 |
| 80 A | 100 A | 4 | 4 | 2 | 1 | 1/0 | 2/0 |
| 100 A | 125 A | 2 | 2 | 2 | 1/0 | 2/0 | 3/0 |
| 125 A | 175 A | 1/0 | 1/0 | 1/0 | 2/0 | 3/0 | 4/0 |
| 150 A | 200 A | 1/0 | 1/0 | 1/0 | 3/0 | 4/0 | Split it |
| 200 A | 250 A | 3/0 | 3/0 | 3/0 | 4/0 | Split it | Split it |
| 250 A | 350 A | Split it | Split it | Split it | Split it | Split it | Split it |
24 V chart
| Amps | Fuse | 3 ft | 5 ft | 10 ft | 15 ft | 20 ft | 25 ft |
|---|---|---|---|---|---|---|---|
| 5 A | 7.5 A | 14 | 14 | 14 | 14 | 14 | 14 |
| 10 A | 15 A | 14 | 14 | 14 | 12 | 12 | 10 |
| 15 A | 20 A | 14 | 14 | 12 | 10 | 10 | 8 |
| 20 A | 25 A | 14 | 14 | 12 | 10 | 8 | 8 |
| 30 A | 40 A | 10 | 10 | 10 | 8 | 6 | 6 |
| 40 A | 50 A | 8 | 8 | 8 | 6 | 6 | 4 |
| 50 A | 70 A | 6 | 6 | 6 | 6 | 4 | 4 |
| 60 A | 80 A | 6 | 6 | 6 | 4 | 4 | 2 |
| 80 A | 100 A | 4 | 4 | 4 | 4 | 2 | 2 |
| 100 A | 125 A | 2 | 2 | 2 | 2 | 2 | 1 |
| 125 A | 175 A | 1/0 | 1/0 | 1/0 | 1/0 | 1/0 | 1/0 |
| 150 A | 200 A | 1/0 | 1/0 | 1/0 | 1/0 | 1/0 | 2/0 |
| 200 A | 250 A | 3/0 | 3/0 | 3/0 | 3/0 | 3/0 | 3/0 |
| 250 A | 350 A | Split it | Split it | Split it | Split it | Split it | Split it |
"Split it" means even 4/0 cable can't carry that current safely in a bundle: use two parallel runs, a higher system voltage, or have an installer design it.
Inverter cable sizes
Inverters are the biggest draw in most rigs. These assume a 4 ft run and the inverter at full output with a low battery (90% efficient at 12.0 V or 24.0 V).
| Inverter | Current | Fuse | Cable |
|---|---|---|---|
| 1,000 W at 12 V | 93 A | 125 A | 2 AWG |
| 1,000 W at 24 V | 46 A | 60 A | 6 AWG |
| 1,500 W at 12 V | 139 A | 175 A | 1/0 AWG |
| 1,500 W at 24 V | 69 A | 100 A | 4 AWG |
| 2,000 W at 12 V | 185 A | 250 A | 3/0 AWG |
| 2,000 W at 24 V | 93 A | 125 A | 2 AWG |
| 3,000 W at 12 V | 278 A | 350 A | Split the run or go 24 V |
| 3,000 W at 24 V | 139 A | 175 A | 1/0 AWG |
The method
- Fuse. Take the continuous current and multiply by 1.25 (so the fuse carries no more than 80% of its rating), then round up to a standard size. Blue Sea Systems explains why a fuse shouldn't run at its full rating for long.
- Heat. Pick the thinnest wire whose ABYC E-11 rating, for up to three conductors bundled or in conduit with 105°C insulation, is at least the fuse size. That way the fuse always blows before the wire overheats.
- Voltage drop. Check the round trip with ABYC's formula (circular mils = 10.75 x amps x round-trip feet / allowed volts drop) and keep it under 3%. If that needs thicker wire, use it.
- Minimums. Nothing thinner than 14 AWG for a fused branch, nothing thinner than 4 AWG for a battery main.
Runs through the engine bay (alternator to DC-DC charger) use ABYC's lower engine-room rating. The planner and the wiring tool apply exactly this method to your own lengths.
ABYC ampacity table we use
| Wire | mm² | Bundled (up to 3) | Bundled, engine room | Single, free air | Max 12 V run at rating, 3% drop |
|---|---|---|---|---|---|
| 16 AWG | 1.3 | 18 A | 15 A | 25 A | 2.4 ft |
| 14 AWG | 2.1 | 25 A | 21 A | 35 A | 2.8 ft |
| 12 AWG | 3.3 | 32 A | 27 A | 45 A | 3.4 ft |
| 10 AWG | 5.3 | 42 A | 36 A | 60 A | 4.1 ft |
| 8 AWG | 8.4 | 56 A | 48 A | 80 A | 4.9 ft |
| 6 AWG | 13.3 | 84 A | 71 A | 120 A | 5.2 ft |
| 4 AWG | 21.2 | 112 A | 95 A | 160 A | 6.2 ft |
| 2 AWG | 33.6 | 147 A | 125 A | 210 A | 7.6 ft |
| 1 AWG | 42.4 | 172 A | 146 A | 245 A | 8.1 ft |
| 1/0 AWG | 53.5 | 200 A | 170 A | 285 A | 8.8 ft |
| 2/0 AWG | 67.4 | 231 A | 196 A | 330 A | 9.6 ft |
| 3/0 AWG | 85.0 | 270 A | 229 A | 385 A | 10.4 ft |
| 4/0 AWG | 107.2 | 312 A | 265 A | 445 A | 11.4 ft |
Fuse type matters near a lithium battery
A lithium bank can push thousands of amps into a dead short. Put a fuse rated to interrupt that, such as a Class T, within 7 inches of the battery positive. Blue Sea Systems' figures show ANL fuses only blow at about 140% to 266% of their rating, so size an ANL by its blow point, not its label.
Safety first
Fuse every positive wire as close to the battery or bus bar as you can, and use the wire and fuse sizes from a standard table, not a guess. Boats should follow ABYC E-11; anything that touches 120/240 V AC should follow the NEC. Have a qualified installer check any 120/240 V AC or shore power work.
Run the power planner
Battery, solar, charger, inverter, every wire and fuse, and a priced parts list.
Draw your wiring
Drag parts onto a diagram and get gauge and fuse labels on every run.
Questions people ask
What size wire for a 2,000 W inverter at 12 V?
A 2,000 W inverter can pull about 185 A from a 12 V battery. With a 4 ft run that's 3/0 AWG copper on a 250 A fuse by our method. At 24 V the current halves and so does the cable size.
Should the fuse match the wire or the device?
The fuse protects the wire. It must be no larger than what the wire can carry, and large enough that the device's normal current stays under 80% of the fuse rating. When the device maker specifies a fuse, use that size or smaller, as long as the wire can carry it.
Why is this chart thicker than the one that came with my inverter?
Many charts use free-air ratings and allow 10% voltage drop. We use ABYC's rating for wires bundled or in conduit (how they run in a van wall) and hold drop to 3%. Thicker cable runs cooler and wastes less energy; on short runs the cost difference is small.
Is length one way or round trip?
The chart's lengths are one way: from the battery or bus bar to the device. The math doubles it, because current flows out on the positive and back on the negative.
Does the negative wire need to be the same size?
Yes. The negative carries the same current back to the battery, so it gets the same gauge as the positive.
Sources
- ABYC E-11 Tables VI-A and VI-B (105°C insulation), as published by Blue Sea Systems (read 2026-10-22)
- Blue Sea Systems, Choosing Circuit Protection (fuse headroom, ANL blow points)
- ABYC E-11, AC and DC Electrical Systems on Boats (standard)
Keep going
Van electrical basics
The six parts every camper system has, how they connect, and a diagram to download.
DC-DC charger sizing
20 A or 40 A, smart alternators, and what an hour of driving puts back.
Lithium conversion
Swapping lead-acid for lithium: what it costs and the three things that must change with it.
Shore power and EV charging
30 A and 50 A plugs, what they really deliver, and charging an EV at the campground.