Mulch, sand, stone dust, item 4 and concrete quantities are pretty easy to calculate but, what about stones? Say a customer wants to replace their mulched beds with decorative stone. If we're talking about the small white or red ones it's virtually the same as mulch but, if they want to use 3" river rock then things change because just one rock is greater than the depth that we would usually mulch and you would be able to see the fabric through the gaps. What formula would you use to determine how many yards of 1.5", 2" or 3" stone you would need per square foot. Part 2: Does stone size affect production rates? I use the figure of 1.25 yds per man hour for mulch and 1 yd per man hour for the 1/4" stone so I would guestimate that as the stone size increases the production rate decreases- does it?