An RV wire-size chart is useful for comparing conductors, but the correct purchase needs ampacity, total circuit length, voltage drop, equipment requirements and protection to be checked together.
The table below gives approximate copper cross-sectional areas. It deliberately does not assign one universal fuse or load to each gauge: those decisions depend on how the circuit is installed.
AWG reference chart
| AWG | Approximate conductor area, mm² |
|---|---|
| 16 | 1.31 |
| 14 | 2.08 |
| 12 | 3.31 |
| 10 | 5.26 |
| 8 | 8.37 |
| 6 | 13.3 |
| 4 | 21.2 |
| 2 | 33.6 |
| 1/0 | 53.5 |
| 2/0 | 67.4 |
| 4/0 | 107.2 |
Smaller AWG numbers represent larger conductors. An area conversion does not prove that two finished cable products share the same temperature, flexibility, insulation or environmental ratings.
Check current capacity and voltage drop separately
Ampacity concerns conductor temperature under the actual installation conditions. Voltage drop concerns how much voltage is lost in the current path. Cable routing, bundling, ambient temperature, insulation, connections and length all matter.
A circuit can pass a voltage-drop target and still fail an ampacity or equipment requirement. It can also have an acceptable current rating while losing too much voltage over a long run.
For DC wiring context, see Victron's Wiring Unlimited: DC wiring. Use the exact equipment manual and an appropriate installation design rather than treating a generic chart as certification.
Worked voltage-drop example
Assume a 5A load and a 15-foot one-way run, with a separate return conductor of the same length. That is 30 feet, or about 9.14 metres, of conductor in the circuit.
If the chosen cable's declared resistance is 0.0033 ohms per metre, the example gives:
- Circuit resistance: 9.14 × 0.0033 ≈ 0.030 ohms.
- Cable voltage drop: 5A × 0.030 ohms ≈ 0.15V.
- At a 12V supply: about 1.3% cable voltage drop.
This is an illustrative calculation using a stated resistance assumption. Use the actual cable's resistance and conditions, include connection losses, and separately verify ampacity, startup requirements and protection. It is not a blanket instruction to buy a particular gauge for every fridge.
Build an exact cable order
Record the load, supply voltage, current path, required conductor size, cable type, insulation rating, termination sizes and route. Leave physical allowance for secure routing and service without turning an electrical length estimate into a loose or unprotected installation.
For a charger, input current is not necessarily identical to the output-current label. For an inverter, continuous demand, battery voltage, losses and startup behavior need checking. Read the cable and protection instructions for the exact model.
Select protection as part of the circuit
The protective device must suit the conductor and equipment as well as the supply voltage and prospective fault current. A blanket rule such as multiplying every load by the same number is not sufficient for every van circuit.
Do not increase a fuse to cure repeated failures. Use the fuse-troubleshooting guide to identify the cause and verify the correct design before replacing components.
Continue from the calculation to the parts list
Use the US circuit planner to organize the load and cable-run assumptions, then check the output against the exact installation documents. Keep cable, terminals, protection and supports in one electrical parts checklist.
Related: battery cable sizing, DC-DC installation planning and wiring safety guide.
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Jack Kennedy is a self-builder who has built two vans. He created Roam Wired to simplify conversion planning and share free tools, supported by affiliate links.
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