How Much Does An 80lb Bag Of Concrete Cover If Its 4 Inches Thick?

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

An 80lb bag off concrete will cover and area 2' x 2' by just under  2" thick.

A cubic foot of concrete weighs approx. 150 lbs. Per cf. With 27 cf in one cy, a cy of concrete weighs about 4,050 pounds. I'm assuming that you mean ready to use bags of concrete mix.

The 80 lb bag does not include the weight of water while the 4,050 pound cy does include water.

I am estimating that 80 lbs of dry mix would take about 1 gallon of water which is about 8.33 lbs so the weight of the dry mix might be 88 lbs. With water.

So, 88 lbs divided by 4,050 lbs is 0.0217 cubic yards. Or you could say you would need about 46 bags of dry mix plus water to equal 1 cubic yard.

If you are talking about ready mix that comes in a mixer truck, just divide 4,050 by 80.

1 80 lb bag makes 2/3 of a cubic foot. That is equal to 1152 cubic inches. Divide by 4 and get 288 square inches. That equates to approx. 2 square feet in Area. So 1 80 lb. Bag will cover a volume of 4inches thick by two feet wide by one foot long. Or any variation of 2 square feet of top surface area.

400 square feed by 4 inches how many 80pound bags needed