DC Wire Size Calculator

Why DC Wire Size Matters

Undersized DC conductors overheat and waste energy as voltage drop. Oversized wire costs more and is harder to route. Choosing the right AWG balances ampacity, run length, and acceptable voltage drop.

DC Voltage Drop Formula

For a two-wire DC circuit (out and return):

$$V_\text{drop} = 2 \times I \times R \times L$$

$I$ is current in amperes, $R$ is resistance per unit length (Ω per 1000 ft from the AWG table), and $L$ is one-way conductor length. The recommended wire is the smallest gauge that meets both ampacity and your maximum drop percentage.

Real-World Applications

DC wire sizing is essential for solar arrays, RV and marine 12 V systems, battery banks, electric vehicles, and off-grid power distribution where voltage sag directly affects equipment performance.

Frequently Asked Questions

What voltage drop percentage should I use?

Many DC installations target 2–3% drop for critical loads. Less sensitive circuits may allow 5%. Lower drop requires thicker wire.

Is the length one-way or round-trip?

Enter one-way distance. The calculator doubles it internally for the out-and-return path in the voltage drop formula.

Copper vs aluminum?

Copper has lower resistance and higher ampacity per gauge. Aluminum is lighter and cheaper but needs a larger gauge for the same performance.

Does this replace the NEC code?

No. This is a planning tool. Always follow local electrical codes, temperature derating, conduit fill, and installation conditions.

Why does no wire appear?

Very long runs, high current, or strict drop limits may require wire larger than the table provides. Reduce length, lower current, or relax the drop limit.

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Why DC Wire Size Matters

DC Voltage Drop Formula

Real-World Applications

Frequently Asked Questions

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