Sonotube Calculator
Bags and yards for round cardboard forms — Sonotube, Quik-Tube and the like — used for deck piers, post footings and columns. Enter the tube’s inside diameter and the poured height, then how many. Most deck jobs are a bag count; a dozen 12″ tubes at 4 ft is a short load.
Buy 35 × 80 lb bags — under 1 yd³ bagged mix beats a short load.
- Net volume (18.8 ft³)
- 0.70 yd³
- Waste 10%
- + 0.07 yd³
- Ready-mix ticket
- 1.00 yd³
- Approx. weight
- 2,827 lb
- 80 lb bags
- 35
- 60 lb bags
- 47
- 40 lb bags
- 70
- Materials + delivery$5.50–$8 / bag · Sep 2026
- $193 – $280
- Installed (with labor)typ. $535
- $384 – $779
Quantities follow the ticket. Links may earn us a commission at no cost to you; they never change a number.
How to calculate sonotube by hand
Cubic feet per tube = π × (Diameter (in) ÷ 24)² × Height (ft) · 80 lb bags = ft³ ÷ 0.60
Worked example
- Radius: 12 in ÷ 2 = 6 in = 0.5 ft.
- Per tube: π × 0.5² × 4 ft = 3.14 ft³.
- Six tubes: 3.14 × 6 = 18.8 ft³; with 10% waste 20.7 ft³ = 0.77 yd³.
- Bags: 20.7 ÷ 0.60 = 35 × 80 lb bags (about 6 per tube) — under 1 yd³, so bags.
- 8″ tube
- 0.35 ft³ per ft · 0.6 × 80 lb bags per ft
- 10″ tube
- 0.55 ft³ per ft · 0.9 bags per ft
- 12″ tube
- 0.79 ft³ per ft · 1.3 bags per ft
- 16″ tube
- 1.40 ft³ per ft · 2.3 bags per ft
Questions crews ask
How many bags of concrete for a 12-inch Sonotube?
A 12″ tube holds 0.785 ft³ per foot of height, so a 4 ft pour is 3.14 ft³ — about 5.2 × 80 lb bags, or 6 with waste. Per foot of 12″ tube figure 1.3 × 80 lb bags, 1.75 × 60 lb or 2.6 × 40 lb.
How much concrete does a Sonotube hold?
Volume = π × radius² × height. Per foot of height: 8″ tube 0.35 ft³, 10″ 0.55 ft³, 12″ 0.79 ft³, 14″ 1.07 ft³, 16″ 1.40 ft³, 18″ 1.77 ft³, 24″ 3.14 ft³. Multiply by height in feet and divide by 27 for yards.
What size Sonotube for deck posts?
8″ tubes for light decks with 4×4 posts, 10–12″ for 6×6 posts and most residential decks, 12–16″ where the pier carries a beam splice or a hot tub. Many codes want a bell or a wider footing pad below frost depth under the tube.
How deep should a Sonotube go?
Below the local frost line — 12″ in the South to 48″+ in the northern US — plus 6″ above grade so the post base stays dry. The calculator wants the total poured height, which usually includes an 8–12″ footing pad under the tube.
Bags or ready-mix for Sonotubes?
Bags up to about 45 (one yard); above that, or a dozen 12″ tubes at 4 ft, a short load of ready-mix is faster and often cheaper. Pour and rod each tube in one go — a cold joint halfway up a pier is a weak pier.