Formula used
Concrete = π × (hole diameter ÷ 2)² × hole depth × post count × allowance factor
Worked fence post depth example
Fence Post Depth Calculator example: 17 holes × π × (13.7 in ÷ 12 ÷ 2)² × (36 in ÷ 12) = 52.21 ft³. After 10% allowance, the estimate is 2.13 yd³.
From calculated volume to an order
Use bag counts for hand mixing and cubic yards only when the total is large enough for a feasible ready-mix placement.
Where a concrete takeoff can drift
Bell-shaped bottoms, auger overbreak, soil collapse, post displacement, gravel at the base, and above-grade crowns change concrete volume.
Questions specific to this calculation
Does this calculator choose a safe fence-post depth?
Enter the actual hole diameter and depth plus the number of identical posts. Calculate end, gate, or corner holes separately if their sizes differ.