Square kilometer: Square kilometer (symbol km2) is the metric unit of area, which is defined as "the area of a square with a side length of 1km".

1 ha = 1 10,000 m2

Hectare: The unit symbol of hectare is "hm2", where hm stands for 1 00m and hm2 stands for the square of100m (in English, square), that is, 10000 square hetometer, that is,1hectare.

1 m2 = 100 square decimeter

Square meter: Square meter is the metric unit of area. It is defined as the area of a square with a side length of 1 m. In life, square meters are usually referred to as "square meters" or "squares" for short. Hongkong and Taiwan Province are called "square meters".

1 square decimeter = 100 square centimeter

Square decimeter: Square decimeter (with the symbol d㎡) is the metric unit of area and is defined as "the area of a square with a side length of 1 decimeter".

1 cm2 = 100 mm2

Square millimeter: Square millimeter (with the symbol of mm ㎡ 2) is the metric unit of area, which is defined as "the area of a square with a side length of 1mm".