How to Calculate the Concrete Needed for a Footing & a Slab

Concrete can be molded into any shape.

Concrete is a durable material -- it can withstand inclement weather and is not vulnerable to pests or weeds like other materials. Before beginning a project with concrete, it is important to know exactly how much of the product you will need. Miscalculating can result in an additional delivery charge, not to mention having to halt your project.

Instructions

1. Measure the length, width and depth of the space that will be occupied by the concrete footing.

2. Multiply your calculations to figure out the volume of the space. For example, if your footing is 20 feet long, 3 feet wide and .42 feet (5 inches) deep, your total volume is 25.2.

3. Divide the volume by 27 -- the total number of cubic feet in one cubic yard. Because concrete is sold by the cubic yard, converting your calculations to this measurement will enable you to know how many bags to order.

4. Repeat steps 1 through 3 to determine how many cubic yards are needed for the concrete slab. Add the calculations for the footing and slab together to determine the total cubic yards of concrete needed.

5. Add about 10 percent to your total to account for spillage or other errors that may result in a loss of material.

References

• The Family Handyman: How to Estimate a Concrete Order
• Conrock: Key Reasons to Build with Concrete