Concrete Column and Pier Calculator

How it works

A round pier poured in a tube form is a cylinder: its volume is π × radius² × height, with the radius half the tube's inside diameter. A square pier is side × side × height. Diameter and side are entered in inches and converted to feet, so the volume comes out in cubic feet.

The volume of one pier is multiplied by the number of piers and converted to cubic yards (27 cu ft per yard). The waste allowance is added for the amount to order and the bag count, which divides the volume with waste by the yield of one bag and rounds up to whole bags.

The table lists the concrete in one foot of height for common tube diameters, from the same π × r² formula, and how many bags of the chosen size that foot takes. A pier's volume is that figure times its height.

Formula

round pier (cu ft)  = π × (diameter ÷ 24)² × height
square pier (cu ft) = (side ÷ 12)² × height
total (cu yd)       = pier volume × count ÷ 27
to order            = total cu yd × (1 + waste ÷ 100)
bags                = ⌈ pier volume × count × (1 + waste ÷ 100) ÷ yield per bag ⌉
yield per bag: 40 lb ≈ 0.30, 60 lb ≈ 0.45, 80 lb ≈ 0.60 cu ft (QUIKRETE No. 1101, rev. Oct 2022)

Example

Four round piers in 12 in tube forms, each 4 ft tall: one pier is π × 0.5² × 4 = π ≈ 3.142 cu ft, so four are 12.57 cu ft, or 0.47 cu yd.

With 10% waste that is 0.51 cu yd to order. In 80 lb bags, 12.57 × 1.1 = 13.82 cu ft ÷ 0.60 = 23.04, so 24 bags. The table shows a 12 in tube holds 0.785 cu ft per foot, 1.31 bags of 80 lb mix.

Assumptions and limitations

• Piers are straight-sided: a cylinder of the tube's inside diameter, or a square prism. Bell or flared bottoms, spread footings under the pier and holes dug wider than the form are not included and need to be added separately.
• The tube diameter entered is the inside diameter. Nominal and actual form diameters can differ slightly by manufacturer.
• Bag yields are the approximate figures on the QUIKRETE Concrete Mix No. 1101 data sheet (revised October 2022): 0.30 cu ft per 40 lb bag, 0.45 per 60 lb and 0.60 per 80 lb. Other brands and mixes yield differently and the bag label governs.
• The waste allowance is a typical figure and is editable.
• This is a material estimate, not engineering. Pier diameter, depth, reinforcement and footing size depend on the load, the soil and the frost depth and are set by the applicable building code, the building official or a licensed engineer; the result is not a code determination.

Frequently asked questions