DC Wire Gauge Calculator

Estimate a wire gauge for 12V, 24V, or 48V DC projects based on current, one-way wire length, wire material, and target voltage drop.

Enter Your DC Wire Run

Common setup preset

Presets are examples. Use your actual current, wire length, and voltage when possible.

System voltage (V)

Examples: 12V, 24V, or 48V DC.

Load current (amps)

Use the expected running current, not just the device wattage.

One-way wire length (feet)

Use distance from power source to load. The calculator accounts for the return path.

Target maximum voltage drop (%)

3% is a common planning target. Some projects may tolerate more or less.

Wire material

Aluminum has higher resistance than copper at the same gauge.

Compare a specific wire size

Use this to compare voltage drop on a wire size you are considering.

Current buffer (%)

Adds current headroom before selecting a wire size by voltage drop.

Use time (hours)

Optional. Used to estimate energy lost as heat in the wire.

Your Results

Suggested wire size

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Enter values and calculate.

Estimated drop

—

For the suggested wire size.

Voltage at load

—

Estimated voltage reaching the device.

Compared wire size

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For the selected comparison wire.

This calculator estimates wire size by voltage drop only. It does not approve wire ampacity, fuse size, insulation type, temperature rating, installation method, or code compliance.

How to Use This DC Wire Gauge Calculator

Enter the system voltage, load current, one-way wire length, wire material, and target voltage drop. The calculator estimates the smallest listed wire size that meets the voltage drop target.

This tool is mainly for low-voltage DC planning, such as 12V lighting, small battery systems, controllers, actuators, accessories, and workshop projects. It is not a substitute for electrical code, ampacity tables, fuse sizing, or professional electrical design.

Formula Used

Adjusted amps = load amps × (1 + current buffer %)
Round-trip wire length = one-way length × 2
Wire resistance = ohms per 1,000 ft × round-trip length ÷ 1,000
Voltage drop = adjusted amps × wire resistance
Voltage drop % = voltage drop ÷ source voltage × 100
Voltage at load = source voltage − voltage drop

Example Calculation

A 12V device drawing 10 amps over a 15-foot one-way wire run has a 30-foot round-trip current path. That round-trip length matters because current must travel out to the load and back to the source.

At low voltage, even a small voltage drop can be noticeable. A drop of 0.6V on a 12V system is 5%, while the same 0.6V on a 120V system is only 0.5%.

Common Wire Gauge Mistakes

Using the one-way distance but forgetting the return path.
Choosing wire only by voltage and ignoring current.
Assuming low voltage always means low risk or low current.
Using voltage drop as a substitute for fuse sizing or ampacity rules.
Ignoring connector ratings, insulation type, wire temperature, and installation conditions.
Running high-current 12V loads through wire that is too small for the job.

Important Safety Note

Use this calculator as a planning tool only. It estimates wire size for voltage drop, not whether the wire is safe or code-compliant.

Do not use this calculator as permission to overload a wire, battery, fuse, connector, controller, inverter, charger, power supply, outlet, or circuit. For mains wiring, permanent circuits, breaker panels, sparks, heat, burning smells, exposed conductors, or code-sensitive work, stop and contact a qualified electrician.