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How many 80 lb bags of concrete do I need for 1 yard?

The finished volume of an 80# bag of Sacrete or Quikrete (pre-mixed cement, sand and gravel) is 0.6 cubic foot (stated on the bag).

There are 27 cubic feet in a cubic yard. Dividing 27 cubic feet by the volume of the bag will give you the number of bags you need.

An 80# bag of Sacrete yields 0.6 cf of concrete
27 cf / 0.6 cf = 45 bags per cubic yard

FYI;

A 60# bag of Sacrete yields 0.45 cf of concrete
27 cf / 0.45 cf = 60 bags per cubic yard

A 50# bag of Sacrete yields 0.38 cf of concrete
27 cf / 0.38 cf = 71.1 bags per cubic yard

A 40# bag of Sacrete yields 0.30 cf of concrete
27 cf / 0.30 cf = 90 bags per cubic yard

As an example: If you needed 1.35 cubic yards of concrete and you wanted to mix it by hand (heaven forbid) using 80# bags:

(1.35 cubic yards * 27) / 0.6 cf = 61 - 81# bags of Sacrete needed . . .

. . . plus a couple of extra bags, just in case (you can take them back afterwards if not needed) and . . .

. . . a lot of sweat and an adequate supply of water (some to hydrate the concrete, some to drink and most to pour over yourself before you finish the job)!

George