Undersized DC wire heats up and sags voltage at the inverter or controller. This DC cable size calculator takes current, one-way length, and bus voltage to suggest a conservative AWG with an estimated drop percentage for planning.
Benefits
- Picks AWG from ampacity tables for your load current.
- Checks ~3% voltage drop over the run length.
- Works for 12 V, 24 V, and 48 V battery buses.
How it works
- Enter steady or peak DC load current in amps.
- Add one-way cable length in feet and system voltage.
- Read recommended AWG and approximate voltage drop %.
FAQ
How does a DC cable size calculator work?
It selects the smallest standard AWG that carries your amps per conservative ampacity tables, then estimates voltage drop over round-trip resistance (out and back). Example: 40 A, 20 ft one-way, 12 V often lands near 4–6 AWG depending on drop target—verify with the tool for your exact inputs.
One-way or round-trip length?
Enter one-way distance from battery to load. Drop math doubles the length internally for positive and negative conductors. Measuring only half the loop understates resistance and oversizes wire optimistically.
When should I go one AWG size larger?
Inverter surge, lithium charge spikes, or long runs near 3% drop often warrant the next size up. Aluminum conductors need larger gauge than copper. Follow local electrical code for final installs—this calculator is for planning estimates.
Technical specifications
- Input: load_A, one-way_length_ft, system_V.
- Output: recommended AWG + ~% voltage drop.
- Drop uses round-trip copper resistance.
- Related: dc-cable-size, dc-cable-voltage-drop, watts-to-amps.