Hi Cameron,

There are 43560 square feet in an acre so one acre covered with half a foot of soil would give a volume of $\large \frac{43560}{2} = 21780$ cubic feet.

To calculate the number of pounds of dirt that would be you need to know the density of the dirt. The place where I look for the density of a dry material is the SImetric site. Go to their page and look in the list under earth. You will see that there are different values depending on the type of dirt you have. Select the one you think is most appropriate and copy its density. I am going to use dense earth although I don't expect that is what you have. The density given is 2002 kilograms per cubic metre. I then went to Google and typed in 2002 kilograms per cubic metre in pounds per cubic foot. Google responded with (2002 kilograms) per (cubic meter) = 124.980777 pounds per (cubic foot). The number of pounds of dense earth in 21780 cubic feet is then $21780 \times 124.98.$

Penny