Wire Sizing Matters
Voltage drop is the voltage lost along conductors before power reaches the load. A small drop is normal. A large drop can heat wires, dim lights, slow motors, and waste energy. Good design keeps the drop within a chosen limit. Many designers use three percent for branch circuits. They often use five percent for the whole feeder and branch path.
What This Tool Checks
This calculator compares voltage, current, distance, phase, material, temperature, power factor, and parallel runs. It also checks a selected wire against a target drop limit. Then it finds the smallest listed conductor that meets the drop target and an ampacity check. The ampacity values are planning references. Local codes, insulation ratings, terminals, conduit fill, bundling, and ambient conditions can change the final answer.
Better Inputs Give Better Results
Use one way circuit length. Do not enter the round trip length. The formula adds the return path for single phase and direct current circuits. For three phase circuits, it uses the square root of three factor. Enter the real load current, not just breaker size, unless breaker loading is your design basis. For continuous loads, increase the load percentage when your code requires it.
Copper And Aluminum Choices
Copper has lower resistance than aluminum. It usually allows a smaller conductor for the same voltage drop. Aluminum is lighter and may cost less for feeders. It often needs a larger size and correct terminations. Temperature also matters. Resistance rises as conductors warm. A hotter conductor creates more drop and more losses.
Using Results In Design
Start with the recommended wire size. Review the selected wire result too. If it fails, increase conductor size, reduce length, raise voltage, add parallel runs, or lower load current. Check the calculated power loss. High loss can make a compliant design expensive to operate. Always verify the final conductor with an electrical code table and a qualified professional. This tool supports planning. It does not replace engineered approval for critical work.
Document assumptions before buying cable. Save the CSV for estimates. Save the PDF for review notes. Compare several limits when equipment is sensitive. Motors, pumps, welders, and long outdoor runs may need stricter planning margins and future maintenance records.