Solar Wire Size Calculator

Our free Solar Wire Size Calculator helps solar installers, electricians, and DIY off-grid builders select the correct AWG copper cable for any DC solar circuit. Proper wire sizing is critical for safety, efficiency, and code compliance. Undersized wire creates excessive voltage drop that reduces charging efficiency, causes overheating, and can be a fire hazard. This tool uses the standard copper resistivity formula (ρ = 0.0172 Ω·mm²/m) with round-trip cable length to compute resistance, voltage drop percentage, and power loss in watts for every AWG size. It automatically identifies the minimum AWG wire that keeps voltage drop within your specified limit — defaulting to the 3% maximum recommended by NEC for solar PV systems. The full AWG comparison table from AWG 14 through 4/0 shows voltage drop percentage and power loss for each size, giving you complete visibility into the trade-offs between wire cost and efficiency. Metric (meters) and imperial (feet) input units are supported. System voltages of 12V, 24V, and 48V are covered — the calculator correctly shows how higher system voltages dramatically reduce voltage drop for the same current and cable length. This browser-based solar wire sizing tool requires no registration and processes all calculations locally for complete privacy. It is suitable for sizing battery-to-inverter cables, solar panel home-run wires, charge controller connections, and any DC circuit in a photovoltaic system. Always verify your final wire selection against local electrical codes and ampacity tables, which account for bundling, conduit fill, and temperature ratings beyond voltage drop alone. This free tool is your first step toward a safe, efficient solar wiring installation.

This tool is part of our collection of 100+ free online utilities designed to help developers, designers, and professionals work more efficiently. All tools are completely free, require no registration, and process data locally in your browser for maximum privacy and security. We continuously update and improve our tools based on user feedback to ensure they meet the evolving needs of our global community. Whether you're working on personal projects, professional tasks, or educational assignments, our tools provide reliable solutions that respect your privacy and deliver instant results. The intuitive interface makes it easy for beginners to get started while providing advanced features for experienced users. All tools include comprehensive documentation, example data, and helpful tips to ensure you get the most out of every utility. We believe in making powerful tools accessible to everyone, regardless of technical expertise or budget constraints.