Do you know of a site that lists not only perennial height, but also width?

Question:I'm planting two very small perennial flower beds (one 7x3 the other 14x3) and I'm afraid I bought too many plants. Roughly how many plants do I need per bed?

Answers:
In that I don't know what plants you have, you could check them out at the Cornell University Flower Growning Guides.