About this calculator
Concrete for deck footings, pergola piers, porch columns and pad foundations. Works for round cardboard form tubes and square dug pads.
How it’s calculated
Round: π × (diameter ÷ 2)² × height. Square: side A × side B × height. Multiply by the number of piers, then add waste.
Worked example
With these inputs:
- Shape
- Round (tube)
- Diameter
- 12 in
- Height / depth
- 4 ft
- Number of piers
- 8
- Supply as
- Pre-mixed bags
- Bag size
- 30 kg
- Waste allowance
- 10%
the result is:
- Concrete needed
- 0.78 m³
- Per pier
- 3.1 cu ft
- Ready-mix order (to 0.25 m³)
- 1 m³ (1.31 cu yd)
- 30 kg bag
- 56 bags
- Approx. wet weight
- 1.88 t
Tips from the trade
- A bell or spread footing at the base adds volume. Add it as a separate square pad calculation.
- Dug holes are wider than the tube. If you pour straight into the ground, measure the hole, not the tube size.
- Footings must go below frost depth: often 4 ft (1.2 m) in much of Canada, and deeper on the Prairies and in the North. Check your municipality’s figure.
Common questions
How many bags for a 12-inch pier?
A 12" × 48" tube holds about 3.1 cu ft (0.089 m³), roughly seven 30 kg bags with waste.
Results are estimates for planning and pricing. Check quantities against your drawings, the manufacturer’s data and the building code adopted in your province before ordering.