Wire size calculator
This is not an ampacity calculation. It does not tell you whether a wire can safely carry the current. It does not include ampacity, temperature derating, bundling, terminal temperature, or conduit fill. After you have a suggested size, you must still check that size against the local codebook for current-carrying capacity.
Enter the one-way length — the path the cable actually takes. Do not multiply that length by 2.
How the wire size calculator works
Results from these calculators are for learning and estimation only. They are not a substitute for a licensed electrician, a licensed HVAC contractor, the local codebook, or manufacturer instructions. The electrical tools use a DC-resistance method and do not calculate ampacity, derating, conduit fill, reactance, or power factor. The BTU tool is only for U.S. room window air conditioners, not central systems, and does not replace a professional load calculation. The methods are written for U.S. practice and are not directly applicable outside the United States. If you use these results, you do so at your own risk.