12 Volt Wiring Size Chart

Find the correct wire size for any 12V project with easy-to-read tables for 3% and 10% voltage drops.

$9.18 USD

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Material Ultra-durable waterproof greaseproof paper

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Easily Find the Right 12V DC Wire Size

Avoid the risks of improper wiring, such as equipment damage or fire hazards. The 12 Volt Wiring Size Chart is your trusted solution for selecting the correct wire size for any 12V DC project—whether on your boat, in your car, or for your RV. With large, easy-to-read shaded charts for both 3% and 10% voltage drop, you can size wires accurately and efficiently every time.

Includes detailed tables for both regular and engine-room installations
Durable, waterproof, and grease-proof design stands up to tough environments
Compact size, perfect for toolboxes, lockers, or workbenches

How to Use • Step-by-Step with Pictures

How to Use The Boat Galley 12 Volt Wiring Size Chart Step 1: check the amerage of the 12v appliance you're wiring.

How to Use The Boat Galley 12 Volt Wiring Size Chart Step 2: Measure the distance from the batteries to the item as the wire will go (not in a straight line)

How to Use The Boat Galley 12 Volt Wiring Size Chart Step 3: Decide if you need the 3% of 10% voltage tables, using the criteria printed on the chart

How to Use The Boat Galley 12 Volt Wiring Size Chart Step 4: Find the right table for the allowable voltage drop and whether the wire goes through the engine compartment or not.

How to Use The Boat Galley 12 Volt Wiring Size Chart Step 5: use the chart to determine the minimum size wire needed. Shaded lines make it easy to determine.

How to Use The Boat Galley 12 Volt Wiring Size Chart Step 6: An important reminder that wire gets larger as the gauge number gets smaller. Using larger wire is never a problem but using too-small wire can cause performance problems and is a serious fire risk.

Includes More Than Just Wire Sizes

Wiring connector sizes and color codes
Battery state of charge chart
Simple formulas for watts, amps, and volts

Made in USA • Built to Last • Environmentally Friendly

Designed in the USA; printed in the USA on American-made recyclable synthetic paper using environmentally-friendly soy-based inks at a facility that is completely wind-powered. Minimal packaging. Tough enough to handle life on a boat, it won’t tear, degrade, or smear, even in humid or greasy conditions.

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At The Boat Galley, we have one mission: to help you cruise with confidence.

As liveaboard cruisers, we understand the challenges and questions that come with boat life. That’s why we create practical products and courses designed to tackle the same issues we’ve faced ourselves—making your life on the water easier, safer, and more enjoyable.

Try our products and courses for yourself. If they don’t make your boat life better, use our 90-day FREE no-hassle return guarantee.

Raved About By TheatreCat . . .

"Very handy to have onboard for quick reference."

Verified Purchaser, 12 Volt Wiring Size Chart

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Meet The Boat Galley Team

At The Boat Galley, we’re all cruisers. We know the joys—and the challenges—of boat life. The steep learning curve, costly mistakes, and hours spent searching for answers can be overwhelming. We’ve been there. That’s why we’ve created practical tools, trusted resources, and real-world guides to help you skip the frustrations and focus on enjoying your cruising life.