VoltCheck24 Engineering Calculator

12V Wire Size Calculator for Battery, RV, Marine, and LED Wiring

Estimate 12V DC wire size for battery loads, RV accessories, marine devices, LED strips, and low-voltage equipment.

Open Interactive Calculator Open AWG to mm2 Wire Table

How to use this calculator

Collect the values below from the equipment nameplate, data sheet, or field measurement.
Enter values using one consistent unit system and use worst-case operating conditions.
Review the result, margin, and engineering note before selecting hardware.
Cross-check the result with the related calculator and save the review for your project record.

Input checklist

12V source voltage range
Load current and fuse size
Battery-to-load cable length
Allowed drop for lights, pumps, or electronics

Example field question

Use this calculator when a design review or site issue requires a quick engineering check before a detailed manufacturer selection.

Common mistakes to avoid

Do not mix nominal values with measured worst-case values. Keep units consistent and include cable, temperature, duty, and derating assumptions where applicable.

Standards and validation

Review the result against local codes, IEC/NEC/NFPA/ISO practices when applicable, project specifications, and the latest manufacturer data sheet.

Recommended workflow

Start with the primary calculation, then use the related tool to check the next design dependency. Save or print the result only after the assumptions and worst-case conditions are confirmed.

Start with the primary inputs Check the related dependency

Formula and Inputs

At 12V, the same absolute voltage drop is a larger percentage of the system voltage, so conductor sizing becomes more sensitive to distance and current.

Industrial Use Cases

Use this calculator for 12V batteries, DC lights, pumps, fans, small inverters, vehicle accessories, and short low-voltage wiring runs.

Engineering Note

Automotive, RV, and marine installations can require specific cable insulation, fuse placement, flame rating, and environmental protection. Verify against the applicable rules.

FAQ

Why is 12V wiring sensitive to voltage drop?

A 0.6V drop is already 5% of a 12V system, so long cable runs often need larger conductors.

Where should the fuse go in a 12V circuit?

Place overcurrent protection close to the source according to the applicable vehicle, marine, or electrical standard.

Preliminary engineering reference only. Confirm final selections against current standards, project specifications, and manufacturer data.