Battery Cable Size Calculator
// SCREEN DC BATTERY AND INVERTER CABLE SIZES FROM CURRENT, ONE-WAY LENGTH, CONDUCTOR MATERIAL, AND ALLOWABLE VOLTAGE DROP //
Low-voltage DC systems often need larger conductors because the allowed voltage-drop budget is small.
Enter the expected continuous DC current on the cable run.
Enter the one-way distance. The tool doubles it automatically for the full DC circuit path.
Copper is more common for battery and inverter cables; aluminum needs larger sizes and compatible terminations.
A 2% to 3% target is common for sensitive battery and inverter circuits.
26.7 mm2 equivalent
This conductor clears both the ampacity screen and the selected voltage-drop target.
Estimated from conductor resistance of 0.245 Ω/kft at 20C, scaled over the round-trip length.
Each row checks conductor resistance and basic ampacity against the selected DC load and voltage-drop target.
| Gauge | Metric | Ampacity | Voltage Drop | Resistance | Status |
|---|---|---|---|---|---|
| 14 AWG | 2.08 mm2 | 20 A | 30.7% | 3.07 Ω/kft | Review |
| 12 AWG | 3.31 mm2 | 25 A | 19.3% | 1.93 Ω/kft | Review |
| 10 AWG | 5.26 mm2 | 35 A | 12.1% | 1.21 Ω/kft | Review |
| 8 AWG | 8.37 mm2 | 50 A | 7.64% | 0.764 Ω/kft | Review |
| 6 AWG | 13.3 mm2 | 65 A | 4.91% | 0.491 Ω/kft | Review |
| 4 AWG | 21.1 mm2 | 85 A | 3.08% | 0.308 Ω/kft | Review |
| 3 AWG | 26.7 mm2 | 100 A | 2.45% | 0.245 Ω/kft | Pass |
| 2 AWG | 33.6 mm2 | 115 A | 1.94% | 0.194 Ω/kft | Pass |
| 1 AWG | 42.4 mm2 | 130 A | 1.54% | 0.154 Ω/kft | Pass |
| 1/0 AWG | 53.5 mm2 | 150 A | 1.22% | 0.122 Ω/kft | Pass |
| 2/0 AWG | 67.4 mm2 | 175 A | 0.97% | 0.097 Ω/kft | Pass |
| 3/0 AWG | 85.0 mm2 | 200 A | 0.77% | 0.077 Ω/kft | Pass |
| 4/0 AWG | 107.2 mm2 | 230 A | 0.61% | 0.061 Ω/kft | Pass |
12V inverter feeder
A 12V system at moderate current can require a surprisingly large cable because even a few tenths of a volt becomes a meaningful percentage drop.
24V battery bank interconnect
Doubling system voltage cuts percentage drop in half for the same conductor and current, so 24V systems often size more efficiently than 12V layouts.
48V DC equipment run
At 48V, voltage-drop pressure eases further, but long runs and high inverter currents can still force larger copper sizes.
NEC Chapter 9 Table 8 is a common source for conductor resistance values used in voltage-drop planning.
NEC branch-circuit and feeder guidance is often used as a planning benchmark even when battery systems need additional equipment-specific review.
IEC 60364-5-52 provides an international framework for conductor selection and voltage-drop considerations.
IEC 60228 helps relate conductor classes and nominal cross-sectional areas to practical cable selection.
- Using one-way length in the voltage-drop math without accounting for the return conductor path.
- Treating ampacity alone as the final answer on 12V systems where voltage drop is usually the tighter constraint.
- Selecting aluminum conductors without confirming connector listings, corrosion control, and strand flexibility requirements.
Run a broader voltage-drop check for other circuit types and conductor sizes.
Inspect conductor resistance directly when you want to audit the drop calculation inputs.
Review temperature limits and derating factors before final conductor selection.
Compare this DC-focused screen with a more general wire-sizing workflow.
This tool is a planning screen, not a final engineering approval. Confirm conductor listing, temperature rating, overcurrent protection, terminations, flexible-cable requirements, and manufacturer instructions before installation.