Is there a matrix / table to help with number of units / property size? (each floor is 100 sqm)

I live in a small double story and with my existing router (located in the living room) provides a good signal to the upstairs bedrooms and living room, but the study on the other side is a dead zone.  

I am thinking a 2 unit Deco will do the job -  where the existing router is is and the other in the deadzone. 

thanks