Convert Square Mil (mil²) to Acre (US Survey) (ac (US)) instantly.
About these units
Square Mil (mil²)
A square mil equals the area of a square one mil (0.001 inch) on each side, producing an area of one-millionth of a square inch. This tiny unit appears in microfabrication, thin-film manufacturing, and fine electronic component design. Engineers rely on mils and mil² for PCB trace design, wire bonding pads, and micro-mechanical parts. Despite modern efforts to shift toward metric units, mils remain deeply embedded in American electronics manufacturing due to legacy tooling and engineering standards.
Acre (US Survey) (ac (US))
The US survey acre is based on the US survey foot, making it slightly different from the international acre. With a value of 43,560 survey-square feet, it appears extensively in historical property records and federal land surveys. Because millions of acres in the United States were mapped using PLSS, the survey acre remains necessary for interpreting legal land rights, even though modern mapping often uses metric units or the international foot. This specialized acre illustrates how subtle unit differences can survive for centuries due to legal and administrative inertia.