🧱 Concrete Estimator – Tube
Figure out how much concrete you need to fill round tube forms for footings or posts, in cubic yards and pre-mixed bags.
What this calculator does
The Tube Concrete Estimator calculates how much concrete is needed to fill one or more round tube forms (such as Sonotube) used for footings, deck piers, or fence posts.
The formula
Each tube is treated as a cylinder: Volume = π × r² × height, where r is half the tube diameter. The volume for a single tube is multiplied by the number of tubes to get the total, which is then converted from cubic feet to cubic yards (divide by 27) since ready-mix concrete is typically ordered by the cubic yard.
Bag counts are estimated using common yield figures: roughly 0.45 cubic feet of finished concrete per 60 lb bag and about 0.6 cubic feet per 80 lb bag of pre-mixed concrete. Actual yield varies slightly by brand, so check the bag label for the exact figure.
- Always round up bag quantities and buy a small extra margin for spillage and settling.
- For general planning purposes only; verify footing depth and diameter against your local building code.