Sonotube / Concrete Footing Calculator
Concrete form tubes (Sonotube is the brand everyone uses as the generic name) make deck footings simple โ but guessing the concrete volume wrong means a second trip to the store with wet concrete waiting. Enter your tube size and height and get bags or yards, with waste already included.
How this calculator works
Volume per tube is ฯ ร (diameter รท 2)ยฒ ร height. The calculator multiplies by the tube count, adds 10% waste, and shows the total in cubic feet, cubic yards (for ready-mix delivery), and bags. As a sanity check: one 10" tube at 48" tall holds about 2.2 cu ft โ roughly four 80 lb bags.
Frequently asked questions
How many bags of concrete fill a 10 inch sonotube?
About 0.55 cu ft per foot of height. A 4 ft tall 10" tube holds ~2.2 cu ft, which is four 80 lb bags or five 60 lb bags including a little waste. A 12" tube needs ~0.79 cu ft per foot โ about 45% more than the 10".
How deep should deck footings be?
Below your local frost line โ that ranges from 12" in the South to 48"+ in the upper Midwest and New England. Your local building department publishes the required depth; inspectors check it, so don't guess.
Should I order ready-mix or use bags for footings?
Under about half a cubic yard (โ23 bags of 80 lb), bags are cheaper and simpler. Past that, mixing by hand gets brutal โ most ready-mix plants have a 1-yard minimum, and short-load fees apply, so mid-size jobs often rent a towable mixer instead.