According to the quickrete calculator 80.1 bags. 12' X 12' X 4" = 1.78 yards.

But if we do the math ourselves:

One 80# bag contains 0.6 CUBIC feet (not square feet) of concrete.

1 2/3 (1.66) bags to make a CUBIC foot.

1 cubic yard is 27 Cubic Feet.

1.78 X 27 = 48.06 cubic feet

48.06 CF X 1.66= 79.77 bags

so 80 bags for sure.

Lowes has Quickrete for $3.46 per 80 # bag

80 X $3.46 = $276.80 (plus the cost of your forms)

ready mix delivered is anywhere from 65 to 80 a yard depends on your location. Where I live it is 80 a yard with a 40$ charge for less then 3 yards.

2 yards at $80 plus the $40 small load fee. Add cost of forms. Which you will need to have set and ready when they get there 200 dollars.

(you can order 1.78 yards, they will mix it and bring it to you. Specially formulated for your job but you will pay for 2 yards

call the local concrete company for your exact cost. I hope this has helped

But if we do the math ourselves:

One 80# bag contains 0.6 CUBIC feet (not square feet) of concrete.

1 2/3 (1.66) bags to make a CUBIC foot.

1 cubic yard is 27 Cubic Feet.

1.78 X 27 = 48.06 cubic feet

48.06 CF X 1.66= 79.77 bags

so 80 bags for sure.

Lowes has Quickrete for $3.46 per 80 # bag

80 X $3.46 = $276.80 (plus the cost of your forms)

ready mix delivered is anywhere from 65 to 80 a yard depends on your location. Where I live it is 80 a yard with a 40$ charge for less then 3 yards.

2 yards at $80 plus the $40 small load fee. Add cost of forms. Which you will need to have set and ready when they get there 200 dollars.

(you can order 1.78 yards, they will mix it and bring it to you. Specially formulated for your job but you will pay for 2 yards

call the local concrete company for your exact cost. I hope this has helped