text: what is the measure of how much surface an object has?   surface area   surface area is the area of a given surface. roughly speaking, it is the "amount" of a surface (i.e., it is proportional to the amount of paint needed to cover it), and has units of distance squared. surface area is commonly denoted  for a surface in three dimensions, or  for a region of the plane (in which case it is simply called "the" area).      surface area refers to the summation of the areas of the exposed sides of an object.  units units for measuring surface area include:  square metre = si derived unit  are = 100 square metres  hectare = 10,000 square metres  square kilometre = 1,000,000 square metres  square megametre = 1012 square metres  imperial units, as currently defined from the metre:  square foot (plural square feet) = 0.09290304 square metres.  square yard = 9 square feet = 0.83612736 square metres  square perch = 30.25 square yards = 25.2928526 square metres  acre = 160 square perches or 43,560 square feet = 4046.8564224 square metres  square mile = 640 acres = 2.5899881103 square kilometres  the article orders of magnitude links to lists of objects of comparable surface area.   useful formulae area of a rectangle (and, in particular, a square): length × width  area of a triangle: ½ × base × height  area of a disk: π × r²  area of a sphere: 4 × π × r²  total surface area of a right circular cylinder: 2 × π × r × (h + r)  lateral surface area of a right circular cylinder: 2 × π × r × h  total surface area of a right circular cone: π × r × (l + r)  lateral surface area of a right circular cone: π × r × l