I looked at a bulb vendor's website (Brent & Becky's) and they recommend 4-5 bulbs per square foot, so your garden would need 120-150 bulbs. If you get more than that don't worry because you can plant them pretty close together without anything bad happening. You might know this but tulips are divided into groups according to bloom time. For example, single early, fosteriana, and double earlies are early, and single late, lily-flowering, and double lates are late with triumphs and darwin hybrids in the middle. There are other categories too..look at any online bulb vendor for bloom times. Pick a color scheme and have fun! You might want to layer minor bulbs on top or in the front too..you can enjoy some early crocus before the tulips..

thanks for info. I did not know that about blooming dates. Looking at the sale at BloomingBulbs.com it should only cost me around $45 for the whole bed!