It depends upon what variety seed you have. They vary in height from Mini (’Teddy Bear’) to MONSTER size (’Russian Mammoth’).
https://www.countryliving.com/gardening/g32128958/sunflower-types/
Some of my favorites (Medium sized) for cutting or just enjoying in the garden are:
ProCut Orange
ProCut Gold
Soraya
Ring of Fire
Jung’s carries the above.
Hi Diana, my tomato plants are doing real well so my next question is do I tie them to stakes and at what stage of their growth or do I put one of those tall cages around them? Thanks