Concrete Column Calculator

Formula

cubic yards = π × (diameter in feet/2)² × height × count ÷ 27

Worked example

With Column diameter: 12 in, Column height: 8 ft, Identical columns: 4, Order allowance: 5 %, net concrete is 0.930842 yd³.

Inputs and units

Enter the finished diameter in inches, the cast height in feet, and the number of identical columns. A pad or footing below the column is a different shape and should be estimated separately; do not hide it in the column height.

• Column diameter (in): Measure the finished outside diameter of the cylindrical concrete shaft.
• Column height (ft): Measure only the cast cylinder height, excluding a separate footing.
• Identical columns: Enter the number of columns with these same dimensions.
• Order allowance (%): Use an allowance agreed with the supplier for placement loss and form irregularity.

Calculation and worked example

Convert diameter to feet, halve it to obtain radius, and calculate π times radius squared for one column's cross section. Multiply by height and count to get cubic feet, then divide by 27 for cubic yards. Apply the allowance only to the order estimate In compact notation, cubic yards = π × (diameter in feet/2)² × height × count ÷ 27.

Four columns, each 12 in across and 8 ft tall, have a 0.5 ft radius. Net volume is π × 0.5² × 8 × 4 = about 25.133 ft³, or 0.931 yd³. A 5% allowance gives approximately 0.978 yd³.

How to use the answer

Net volume is the theoretical concrete occupying the forms. The larger order estimate is a planning quantity, not a structural design value; a concrete supplier may require rounding to its delivery increment or minimum order.

For columns of different diameters, run the calculator once per size and add the net yards. Keep the corresponding footings, beams, and slabs in their own estimates before combining the entire pour quantity.

Assumptions and checks

Every counted column is a straight full cylinder with constant diameter. The calculation does not account for reinforcing steel displacement, voids, tapered shafts, over-excavation, or concrete lost during pumping.

The diameter must be halved before squaring; using diameter as radius quadruples the circle area. Also avoid treating inches as feet: a 12-inch diameter is one foot, not twelve feet.

At 12 in diameter and 1 ft height, one column is roughly 0.785 ft³. Multiply that familiar cross-section benchmark by the entered height and column count to check the net result.

Common questions

What does the net concrete result represent?

Net concrete is the geometric volume of all identical cylindrical columns, expressed in cubic yards before placement allowance.

What should I check before relying on this result?

Check form diameter, actual cast height, column count, and how the concrete supplier rounds orders. Estimate each footing independently.