Hi there, Normally a 4rm flat will measure ard 92sqm which u can find commonly in sengkang, punggol and amk etc....92sqm is called 4NG. As for 85sqm, its known for 4s which is the smallest of all 4rm. As for 4A which measure ard 105sqm is the largest in all 4rm and can be commonly found in mature estates like amk, clementi,tamp etc...As for knowing which house size is most suitable, you could choose based on your family size, the estate you prefer and lastly the budget as bigger size comands a higher tag. Hope you hav a clearer view on this area. Warmest regards Ray Lim (Your friendliest realtor in the neighbourhood) 93653729