The square inch (in²) is a small imperial area unit equal to a square measuring one inch on each side, commonly used in engineering specifications, screen size descriptions, and pressure measurements. Piston areas, material stress calculations, and electronic component sizes are frequently expressed in square inches. One square inch equals exactly 6.4516 square centimeters.

The mu (亩) is a traditional Chinese unit of area equal to approximately 666.67 square meters, used extensively in Chinese agriculture, rural land contracts, and property records. Farmland in China is almost always measured in mu, and government policies regarding grain production quotas reference this unit. One mu equals roughly 0.1647 acres or about 7,176 square feet.