Measure from the floor to the top of the seat cushion with nobody sitting on it. That number is your target table height. A table 2 to 5 cm lower still works, because you reach slightly down to a cup; a table more than about 5 cm above the seat forces your elbow up.
Most European and American sofas sit between 40 and 45 cm. That is why the useful coffee-table range is roughly 40 to 48 cm, and why a 55 cm table next to a 42 cm sofa feels like a desk.

