How much concrete does a sonotube need?
A round pier or sonotube holds π × radius² × height of concrete. For a 12-inch-diameter tube (a 0.5-ft radius) 4 feet deep: π × 0.5² × 4 ≈ 3.1 cubic feet, about 0.12 cubic yards. Multiply by the number of piers, then add ~10% for waste and any flared base or footing.
Source: Volume geometry (V = π r² h) · Verify against your AHJ and the adopted code edition.
A sonotube is a cylinder, so the concrete it holds is:
V = π × radius² × height
Work in feet:
- Radius = diameter ÷ 2, converted to feet. A 12-inch tube is 0.5 ft radius; a 10-inch tube is ~0.417 ft.
- Height in feet (the depth of the pour).
- V = π × radius² × height. A 12-inch tube 4 ft deep: π × 0.5² × 4 ≈ 3.1 ft³ ≈ 0.12 yd³.
Then:
- Multiply by the number of piers — a deck on six of these needs ~18.6 ft³ (~0.7 yd³).
- Add ~10% waste, plus extra for any bell/flared base or spread footing at the bottom, which many piers require for bearing.
Bags suit one or two piers; for a whole deck, ready-mix by the yard is usually easier.
Work it out: the concrete takeoff has a round pier/sonotube shape — enter the diameter, depth, and count and it returns cubic yards, cubic metres, and a bag count with waste.