The Bags of Concrete from Volume calculator computes the number of standards size bags of concreted needed to fill a volume (V)
INSTRUCTIONS: Choose the preferred units and enter the following:
Bags of Concrete (nB): The calculator returns the volume in cubic yards and number of bags of concreted to fill the volume.

 40lb bags
 60lb bags
 80lb bags
The Math / Science
A bag of concrete is sold by weight, but it has volume of concrete associated with it. An 80 pound bag creates 0.6 cubic feet of concrete. 60 lb bag creates 0.45 cubic feet, and a 40lb bag creates 0.3 cubic feet.
The formula for the number of bags of concrete is:
nB = V / BS
where:
Functions and data associated with using bags of concrete in different sizes (40lb, 60lb and 80lb) to fill concrete slabs of different shapes (rectangular, round, polygon).
 Concrete Bags from Volume
 Price of Concrete using Bags: Compute the cost of a volume of concrete (e.g., 4.2 cubic yards) using bags of concrete.
 Concrete by 40lb bag: Computes the number of 40 pound bags of concrete and water needed to mix a volume of concrete.
 Concrete by 60lb bag: Computes the number of 60 pound bags of concrete and water needed to mix a volume of concrete.
 Concrete by 80lb bag: Computes the number of 80 pound bags of concrete and water needed to mix a volume of concrete.
 Concrete Bag Volume: Computes the cubic yards of concrete that can be made from a number of bags of concrete.
 Concrete in Rectangle Slab
 40lb bags in a Slab: Computes the number of 40 pound bags of concrete, length of form boards, and water needed for a rectangle (square) slab based on the dimensions of the slab.
 60lb bags in a Slab: Computes the number of 60 pound bags of concrete, length of form boards and water needed for a rectangle (square) slab, footer, sidewalk, driveway or curb.
 80lb bags in a Slab: Computes number of 80 pound bags of concrete, length of form boards and water needed for a rectangle (square) slab.
 Volume of Circular Slab
 40lb Bags a Circular Slab: Computes the volume of a circular slab and returns the number of 40 pound bags needed, the volume in cubic yards, surface area in square feet, circumference in feet, and the water requirement for making the concrete.
 60lb Bags for Circular Slab: Computes the volume of a circular slab and returns the number of 60 pound bags needed, the volume in cubic yards, surface area in square feet, circumference in feet, and the water requirement for making the concrete.
 80lb Bags for Circular Slab: Computes the volume of a circular slab and returns the number of 80 pound bags needed, the volume in cubic yards, surface area in square feet, circumference in feet, and the water requirement for making the concrete.
 Concrete in Polygon Slab: Computes the amount of concrete (volume) in a polygon shaped concrete slab based on the diameter of the slab, number of sides (e.g., 8 for octagon), and depth. It also returns number of bags (40lb, 60lb, 80lb), water required to make the cement, surface area, length of the individual sides and the total length of the form boards.
 Water Needed for Concrete: Computes the amount of water needed to make a volume of concrete.
 Concrete around Circular Post: Computes the volume of concrete including bags of concrete (40lb, 60lb, 80lb) around a number of round posts in a round hole based on the size of the hole and dimensions of the post.
 Concrete around Square Post: Computes the volume of concrete including bags of concrete (40lb, 60lb, 80lb) around a number of square post (e.g., 6x6) in round hole based on the dimensions of the post, depth and width of the round hole.
 Data Items
CAUTION: The pricing information provided is for calculating convenience with NO implied guarantees to the accuracy of the values listed. Authoritative sources should be sought to confirm any value before risking health or wealth on the veracity of the data. Furthermore, Calc gives no guarantee that you will be able to buy products at listed prices or even if they will be available. The data provided is purely a convenience for making estimates, so we repeat, ALWAYS use local pricing and authoritative specifications.