Depends on space, how you want to grow them, vertically or bushing them out. A reasonable equation would be 2-5 plants in a smaller space, 6-10 in a medium space and 8-12 if you have more room. It's hard to know without more specifics of your grow setup.
a good method is to buy a meter that reads lumens if you already have the light, that way you can place this meter at each portion of where you want to grow in the room and determine how many lumens each plant will receive, obviously foliage and angle to light would effect some growth on the plants.