Concrete Column Calculator — Round & Square Columns
Find the concrete volume for round (tube form) or square columns and piers from size, height and count, with volume per column, premix bags and weight.
Columns and piers have a small footprint but a lot of height, so the concrete adds up quickly once there are several of them. This calculator works out the volume of round columns poured in cardboard form tubes and of square or rectangular columns built with timber or steel forms. Enter the size, height and number of columns to get the volume per column, the total to order, the premix bags needed and a size comparison table.
How to use this tool
- Choose US or metric units.
- Pick round or square/rectangular columns.
- Enter the diameter, or the two side lengths, in inches or centimetres.
- Enter the column height in feet or metres and the number of identical columns.
- Use the table to compare other form sizes at the same height.
Formula
Round: V = π × (D ÷ 2)² × H × n · Rectangular: V = a × b × H × n
D is the inside diameter of the form, a and b are the side lengths, H is the height of concrete in each column and n is the number of columns. Convert inches to feet (÷ 12) or centimetres to metres (÷ 100) before multiplying, then add the waste percentage.
Example
Four 12 in round columns 8 ft tall each hold π × 0.5² × 8 = 6.28 ft³, so all four need 25.13 ft³, or 0.93 yd³. With 5% extra that is 0.98 yd³ — about 26.4 ft³, or 44 bags of 80 lb premix. Two square 16 × 16 in columns 10 ft tall hold 17.8 ft³ each, 1.32 yd³ together.
Frequently asked questions
How many bags of concrete fill a 12 in tube?
A 12 in tube holds 0.785 ft³ per foot of height, so each foot takes about 1.3 bags of 80 lb premix. A tube filled 4 ft high holds 3.14 ft³, which is 6 bags.
Does the rebar reduce the concrete needed?
This estimate uses the full formed volume without subtracting reinforcement or other embedded items. If your quantity takeoff deducts them, calculate their actual displaced volume from the drawings instead of assuming a fixed percentage.
What height should I enter?
The full height of concrete in the form, including any part buried below ground, not just the part that shows.
Do I include the footing under the column?
No. Work out the pad or footing with the footing calculator and add the two volumes together.
Sources
Last updated: 2026-10-30