The square inch equals 6.4516 square centimetres exactly. Used in US engineering, tile specifications, stamp areas and pressure conversion (PSI = pounds per square inch). A US letter-size sheet is 93.5 in².
Real-world: A US letter page is 93.5 in². A common US tile is 144 in² (1 ft²). Credit card ≈ 7.1 in².
Read full square inch reference →The hectare equals 10,000 square metres — a square 100 m on each side. It is the global standard for agricultural land, forests, vineyards and large-scale property. 1 hectare is roughly equivalent to 2.47 acres. European farms are measured in hectares.
Real-world: A rugby pitch is 1 hectare. A Bordeaux vineyard parcel is typically 5–10 ha. The Vatican City covers 44 ha.
Read full hectare reference →