Marine Electronics Wire Gauge Calculator

Calculate the copper wire gauge needed to power a remote fuse block or terminal block from your boat's 12V battery. Add your marine electronics, enter the distance from your battery, and calculate the wire size needed to stay below 3% voltage drop.

Marine electronics wiring illustration showing a 12V battery connected by red and black wires to a fuse block supplying multiple marine electronics. Wire length and gauge size are highlighted.
Calculate the wire gauge needed between your 12V battery and fuse block based on the one-way wire distance and total electronics current draw.

1. Battery & Wiring Setup

Enter your battery type and the one-way distance to your fuse block or terminal block.

All calculations use a nominal 12V supply.
One-way distance. Positive and negative wiring are included in the calculation.
Extra capacity for future electronics.

2. Add Your Marine Electronics

Select each device connected to your fuse block. Add as many different devices as needed, and adjust their quantities or estimated amperage.

Total Estimated Current Draw 0.0 A

Device current values are illustrative estimates, not verified manufacturer specifications. Adjust amperage to match your exact equipment.

3. Recommended Wire Gauge

Minimum Copper Wire Gauge — Voltage Drop
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Add your electronics to calculate the recommended wire gauge.

-- Design Current
-- Estimated Voltage Drop
-- Voltage Drop Percentage
-- Round-Trip Wire Length

Wire Gauge Comparison

Compare estimated voltage drop across standard copper wire sizes. Passing the 3% target does not automatically establish safe wire ampacity.

Wire Gauge Voltage Drop Drop % 3% Target

How This Calculator Works

The calculator adds the current draw of all selected electronics and applies your chosen capacity margin. It then calculates voltage drop for the complete positive and negative wire circuit.

For example, a fuse block located 15 feet from the battery has approximately 30 feet of total circuit wiring.

Important: This calculator sizes wire for voltage drop only. It does not verify conductor ampacity, insulation ratings, wire bundling, terminal ratings, or fuse sizing. Verify those using applicable marine electrical standards and manufacturer instructions. Install suitable overcurrent protection near the battery.

Build a Reliable Marine Electronics Power System

Proper wiring, circuit protection, and connections help your electronics perform reliably. Explore our marine rigging supplies for your next installation or upgrade.

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