Formula used
Concrete = π × (hole diameter ÷ 2)² × hole depth × post count × allowance factor
Worked post hole concrete example
Post Hole Concrete Calculator example: 7 holes × π × (13.4 in ÷ 12 ÷ 2)² × (36 in ÷ 12) = 20.57 ft³. After 10% allowance, the estimate is 0.84 yd³.
From calculated volume to an order
Round to whole bags for hand-mixed work; for a large group of holes, check whether ready-mix access and minimum-load charges are practical.
Where a concrete takeoff can drift
Post displacement, auger overbreak, soil collapse, gravel bases, bell bottoms, and above-grade crowns change the concrete placed per hole.
Questions specific to this calculation
Should the post volume be subtracted from the hole volume?
Enter hole diameter, hole depth, and post count for identical holes. Separate gate, corner, and terminal posts when their excavations differ.