YES. First, check how many pieces they pack in a box then use this formula: SqM per box = (0.A * 0.B) * N here... A = length of tile in mm B = width of tile in mm N = number of tiles in a box Let's understand this with an example. If you want 300mm x 600mm tile then put these numbers after decimal point (0.300 x 0.600 = 0.18) Mostly they pack 5 pieces per box of this size tile (so 0.18 x 5 = 0.90) Thus a box of 300x600mm can cover 0.90 Square meters In case if you want to convert this square meter in square ft just multiply it with constant 10.764 (So 0.90 square meter  x 10.764 = 9.687 Square ft) Other examples: 0.600 * 0.600 * 4 = 1.44 0.800 * 0.800 * 3 = 1.92 Now, remember if length or width (or both) are bigger then 1000 mm (i.e. 1 meter) then you need to put the thousand number before the decimal point. e.g. 1.600 * 0.800 * 2 = 2.56 1.200 * 0.600 * 2 = 1.44 For the porcelain slabs which are sold per piece, the square meters can be measured very easily. You just need to get meters of the length & width first. e.g. 1200 / 1000 = 1.2 meters 2400 / 1000 = 2.4 meters Now 1.2 x 2.4 = 2.88 Sq meters per loose slab