Concrete Calculator - Calculator See


Concrete Calculator

Calculate cubic yards and bags of concrete needed for slabs, footings, and columns with custom waste buffer.

Calculator Inputs

ft
Length of pour area.
ft
Width of pour area.
in
Standard residential patio is 4 inches.
%
10% recommended for uneven sub-base.

Calculated Results

Total Concrete Required
2.47 Cubic Yards
60-lb Bags Needed 111 Bags
80-lb Bags Needed 83 Bags
Total Cubic Feet 66.7 cu ft
Values calculate live as you adjust inputs.

About Concrete Calculator

Calculates total volume of concrete in cubic yards and pre-mixed bags for slabs, foundations, walkways, and footings.

What is Concrete Calculator?

Calculates total volume of concrete in cubic yards and pre-mixed bags for slabs, foundations, walkways, and footings.

How to Use This Calculator

  1. Enter slab length and width in feet.
  2. Enter thickness in inches.
  3. Review cubic yards and bag count.

The Mathematical Formula & Variables

Cubic Yards = [Length * Width * (Depth / 12)] / 27 * (1 + Waste / 100)

Step-by-Step Worked Example

Scenario: Slab 20 ft by 10 ft with 4 inch thickness and 10% waste buffer.

  1. Net volume: 20 * 10 * (4 / 12) = 66.67 cu ft.
  2. Divide by 27: 66.67 / 27 = 2.47 cubic yards.
  3. With 10% waste: 2.47 * 1.10 = 2.72 cu yds (or 122 60-lb bags).

Result: 2.72 Cubic Yards (122 60-lb bags)

Frequently Asked Questions

How many 80-lb bags make a cubic yard?

It takes 45 80-lb bags of pre-mix concrete to equal 1 cubic yard (27 cubic feet).