a 10 foot x 9 foot garden= 90sf. a standard cinder block is roughly 17.5" wide by 7.5" high. first measure the perimeter of area to be bordered by blocks. in this case of a 10x9 foot area you would need 38 lineal feet of block. since the block measurement is in inches and your perimeter is in feet you must convert feet into inches. 38 lf x 12= 456 inches divided by the block width 17.5" = approx. 27 blocks. round it up to 28 in case. if you would want to go higher than 7.5 inches high just double the amount of blocks to make it 15" high. you could just do it by having 6 blocks wide by 7 blocks long. as for the dirt to fill it you need to determine how deep you plan to make the bed. for instance a 10 foot x 9 foot garden is 90sf so you will need the third dimension of depth. let's say 1.5 feet deep or 18 inches. 90sf x 1.5 = 135 cubic feet of dirt. hope this helps.

I'm doing the square foot gardening in raised beds, but I'm terrible with math. I need a 90 square food garden, but. I don't know how many cinder blocks I'd need to go all the way around it once. Also for those math geniuses out hue brier, how much potting soil would I need to actually fill the 90 square feet?