Question
I'm building a flower bed in front of my house and would like to know how many 40lbs bags of top soil to use. The total area of the bed is 204sq ft and I would like to have a depth of 7 inches. I will be planting one small tree and the rest of the area will be flowers and maybe a couple small bushes. Thanks!

Answer
Hi Steve, Figuring the volume is easy, you need 119 cubic feet or 4.4 cubic yards of soil.  The problem lies in the top soil. The volume of a 40 lb. bag will depend on what it's made from.  Bark base soils have more volume, peat based soils are heavier and less volume.  You may have to measure one, but a bark based top soil should be around 1 cubic foot or maybe slightly more, so figure about 120 bags.
However, I wouldn't use bagged top soil. I'd find a bulk mulch/soil dealer and buy a blend with mostly your native soil that has been blended with bark,leaf mold and a little sand.  You'll find it grows things better and will be much easier to water.  Jim