Footing for use usually either earth formed, by digging a hole and filling with concrete, or by a heavy duty, round cardboard form (often referred to as Quik-Tube) when the footing is exposed above ground level.

The formula for calculating the volume of concrete for a circular application is
area of the circle (šr²)x height = volume

*make sure all the unit measurements are consistent (in., ft., yd., etc.)

Post and hole measurements reflect diameters. Hole diameter should be 3 times the post diameter.

Calculations for building deck piers/columns:

Assume radius is 0’6” and height is 2’9”. *(convert measurements to feet before continuing)

The calculation for the quantity of concrete is as follows:

pi x radius (squared) x height of footing = Total cubic feet

3.14 x .25 x 2.75 = 2.15 cubic feet

In using the conversions stated above, this calculation would yield the following results:

40 lb. bag 2.15 cubic feet ÷ 0.30 cubic feet/bag = 7.2 (40 lb. bags of concrete) 80 lb. bag 2.15 cubic feet ÷ 0.60 cubic feet/bag = 3.6 (80 lb. bags of concrete)