Wire gauge selection calculator

Enter the load current, one-way cable run, supply voltage, conductor material, and circuit arrangement. The result includes the selected gauge, conductor area, calculated drop, and the minimum area required by the voltage-drop formula. It is a planning calculation, not an ampacity or electrical-code approval, so final conductor selection must also account for installation conditions and applicable regulations.

Start with the electrical load and the complete run

Reliable selection begins with the current that the conductor must carry during the condition you want to evaluate. Enter current in amperes and the physical one-way distance from the source to the load in metres. For a DC or single-phase circuit, the calculator includes both the outgoing and returning conductor in the resistance path, so you should not double the distance yourself. For a balanced three-phase circuit, it applies the square-root-of-three relationship used for line voltage drop. Enter the nominal supply voltage and an allowed percentage drop that reflects the equipment and project requirement. A lower percentage demands a larger conductor because the permitted loss in volts is smaller. Use the expected sustained or design load rather than an optimistic average when continuity of voltage matters. The calculator accepts copper or aluminum and uses each material's resistivity at 20 degrees Celsius. Those inputs establish a clear, reproducible baseline, but conductor resistance generally rises with operating temperature, so a hot installation may experience more drop than this baseline predicts.

How the recommended AWG size is calculated

The allowed loss in volts is the supply voltage multiplied by the chosen percentage. The calculator then rearranges the conductor voltage-drop equation to find the minimum cross-sectional area needed for the specified current and path length. It uses a path multiplier of two for DC or single-phase circuits and the square root of three for balanced three-phase circuits. After computing that minimum area, it examines standard AWG sizes from the thinnest toward the thickest and chooses the first size whose nominal circular area is large enough. This method makes the recommendation conservative with respect to the stated voltage-drop formula: it rounds up to an available gauge instead of presenting a theoretical area that cannot be purchased as an AWG conductor. The result also recalculates resistance and voltage drop using the selected gauge, allowing you to see the margin created by rounding up. AWG numbering runs in the opposite direction from physical size, so a smaller gauge number means a larger conductor; 0, 00, 000, and 0000 continue that progression beyond gauge 1.

Treat voltage drop as one part of conductor selection

A voltage-drop result does not establish that a wire is safe or code compliant. Ampacity can require a larger conductor because allowable current depends on insulation temperature rating, ambient temperature, conductor count in a raceway or cable, installation method, termination ratings, duty cycle, and the rules enforced in your jurisdiction. Protective-device sizing and special requirements for motors, transformers, continuous loads, photovoltaic systems, or battery circuits may also control the final choice. Use this result to answer a focused planning question: which AWG size is large enough for the requested electrical loss under the calculator's stated 20-degree-Celsius resistance basis? Then compare that size with the minimum allowed by the applicable ampacity tables and design rules, choosing the larger conductor whenever those checks disagree. For long runs, consider testing nearby gauges to understand the tradeoff between material cost and delivered voltage. Aluminum conductors also need compatible terminals and installation practices. Have a qualified electrical professional review designs where failure could create fire, shock, equipment damage, or service interruption risks.