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`V = 1/2 * "n" * "r" ^2*sin((2*pi)/ "n" ) * d `

Enter a value for all fields

The **Concrete in a Polygon Slab Volume** calculator computes the amount of concrete (volume) in a polygon shaped concrete slab. * Polygon Slab *

**INSTRUCTIONS:** Choose units and enter the following:

- (
**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 **Bags or STANDARD UNITS**

**Concrete in a Polygon Slab (V):** The volume (**V**) of concrete is returned in cubic yards. However, this can be automatically converted to other volume units (e.g. cubic meters) via the pull-down menu. These are the STANDARD UNITS. For the DIY crowd that mixes their own concrete, vCalc will let the user convert the STANDARD UNITS to the number of bags of concrete in the following sizes:

- 40lb bags
- 60lb bags
- 80lb bags

Once you have your answer in cubic units, CLICK on the STANDARD UNITS button and choose the size of bag (above), and vCalc will tell you how many bags you need for that volume of concrete.

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.