The standard size of aluminum strips used for siding varies by manufacturer and specific product line. However, commonly, aluminum siding is available in widths ranging from 4 to 12 inches and lengths from 12 to 16 feet. The most common widths are 6 and 7 inches, while the standard length is often 16 feet. It's important to check with the specific manufacturer for the exact dimensions of the aluminum siding strips you are considering for your project.