Round concrete columns, deck piers and footings are often poured into cardboard Sonotube forms. Enter the tube diameter, height and how many you are pouring to get the total concrete, and the number of pre-mixed bags if you are mixing it yourself.
Formula
Volume = π × (Diameter ÷ 2)² × Height × Number of columns
Convert the diameter to feet (or metres) first. Divide cubic feet by 27 for cubic yards.
Worked example
Four 12-inch tubes, 4 ft tall: π × 0.5² × 4 = 3.14 ft³ each, 12.57 ft³ in total. With 10% extra that is 13.82 ft³ (0.51 yd³), or 24 bags of 80 lb mix.
Frequently asked questions
How many bags of concrete fill a 12-inch Sonotube?
A 12-inch tube holds about 0.785 ft³ per foot of height, so each foot needs about 1.3 bags of 80 lb mix.
How deep should deck footings be?
Below the local frost line, which ranges from a few inches in warm climates to 4 ft or more in cold ones. Check your local building code.
Last updated · Calculations checked by automated tests· Editorial policy