Generally the bigger the room, the bigger the plank size shall be. Most floating floor board designs range between 140mm and 230mm planks.  Use 140mm-170mm wide planks to help open up smaller areas, while larger rooms look better when using 190mm-230mm planks. If there is a large room using 120mm planks, this will make the floor look extremely busy. If larger than 200mm planks are used in small rooms, it will make the room feel smaller.