the best way to figure it is to calculate the lumens per sq foot
each bulb should be rated for there lumen output.

2000 lumens/sq foot is minimum for plant growth
5000 is average
7000 best.

if you want to keep yeild big and plant small. you should employ some training things like LST topping stuff like that

also the smaller you can get the internodes small. which menas more light.

make sure you are using the correct specturm
6500K for vegg (ie cool white)
2700K for flowering (warm)