Concrete in Polygon Slab

The Concrete in a Polygon Slab calculator computes the cubic yards 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. FORMULA CORRECTION on 6/2024.

INSTRUCTIONS: Choose units and enter the following:

• (n) Number of Sides
• (D) Diameter around Polygon
• (d) Depth of Slab

Concrete in a Polygon Slab (V): The volume of concrete is returned in cubic yards, the surface area in square feet, and the length of one side and the perimeter in feet..  However, these can be automatically converted to compatible units via the pull-down menu. The calculator also computes the equivalent volume in bags of concrete of the following sizes.

• 40lb bags
• 60lb bags
• 80lb bags

The Math / Science

Polygons range from three sided (triangles) on up including rectangles (n=4), pentagons (n=5) and so on.  The user needs to determine the number of sides (n) in the slab to compute the volume. The volume of a slab is computed by multiplying the surface area of the slab by the depth (see diagram).  
The volume of the polygon shaped slab is defined by:

• n - the number of sides of the polygon
• r - the radius from the center of the polygon to a polygon vertex
• d - the depth or thickness of the slab

This equation could be used to estimate the amount of concrete needed for any polygon shaped slab.  vCalc simplifies these equations in several ways for the user.  First, it performs the simple geometry equations for the volume of a polygon shaped object.  Second, it handles different units from small (e.g. cm and inches) to large (e.g. yard, meters even kilometers and miles).   vCalc  also provides automatic conversions for the units of the volume including standard volumes like cubic yards and meters, but it also includes non-standard units that are useful regarding concrete including "number of 40lb bags" needed.  

 The equation generates volume of poured concrete to be delivered or the corresponding number of bags of pre-mixed concrete that would be required to fill the same volume form.

This kind of concrete project could be used for a base for a backyard patio, gazebo, deck, porch, and drive way. 

Bags of Concrete Calculators

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.
• Concrete Mix: Computes volume and weight of cement, sand, gravel and water requires to make a volume of concrete.
• Data Items
  • Cubic Feet of Concrete in a 40lb bag: 0.3 ft³
  • Cubic Feet of Concrete in a 60lb bag: 0.45 ft³
  • Cubic Feet of Concrete in a 80lb bag: 0.6 ft³
  • Retail Concrete Price Survey:
    • Price Survey Date:6/17/24
    • Price Survey Online Store: MULTIPLE
    • Manufacturer: MULTIPLE
      • 80 lb bag: $5.06
      • 60 lb bag: $4.69
      • 40 lb bag: $4.25
      • 10 lb bag: $3.48

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.