Method for working out the amount of concrete required for slabs (together with odd shapes)

Rule of Thumb: add 1/4" to the thickness of your slab for your slab concrete budget. It is assumed that the job is equally graded to the exact depth, and the grade is well compacted.

While examining your grade and it is found that one spot is 4", some spots are 4.5" to 5"-the best solution for both the job quality and your concrete budget is to fix the grade.

Odd shapes: Convert odd shapes into rectangles and odd shapes can be easily figured.

The estimate will be perfect if the figure driveway is 14' x 20' since the driveway is 16' at the top and 12' at the bottom. Through the center the width averages 14'.