Hi Jonathan,

You can use our volume calculator to determine the volume of concrete you will need. The number of bags required depends on what is in the bags. If it is premixed concrete then it should say on the bag how many cubic feet of concrete it will make. If it is not premixed, just cement then you will need to decide what kind of sand and gravel you will use. You need to talk to someone who has done what you plan, using the bags of concrete you have available.

Harley