How much concrete does a 12 inch sonotube hold?

A 12-inch diameter tube holds about 0.79 cubic feet of concrete per foot of depth. At 48 inches deep that is about 3.14 cubic feet, or roughly six 80 lb bags. Doubling the depth doubles the concrete; doubling the diameter quadruples it.

What sizes do sonotubes come in?

Concrete form tubes for DIY decks are most commonly stocked in 6, 8, 10, and 12 inch diameters; the full manufacturer range (Sonotube Round) runs from 6 to 36 inches, with 14, 16, 18, and 24 inch tubes available for heavier piers. Length is cut to the depth you need below the frost line.

How many bags of concrete for one deck footing?

It depends on the tube diameter and depth. A common 10-inch tube 48 inches deep takes about 2.2 cubic feet — four 80 lb bags. A 12-inch tube at the same depth takes about six bags. Use the per-tube bag counts in the chart above.

When should I switch from bags to ready-mix for piers?

Bags win for a handful of tubes because ready-mix trucks have minimum loads. Once total volume passes roughly one cubic yard — about ten 12-inch by 48-inch tubes — price a short-load delivery against the bag count before buying bags.

Sonotube Size Chart: Concrete Per Tube by Diameter & Depth

Concrete per sonotube (cubic feet)

A round pier holds π × (diameter ÷ 24)² cubic feet for every foot of depth. Read the per-foot column for any depth not shown, then multiply. Values are rounded to two decimals.

Tube diameter	ft³ per foot of depth	24″ deep	36″ deep	48″ deep	60″ deep
6″	0.20	0.39 ft³	0.59 ft³	0.79 ft³	0.98 ft³
8″	0.35	0.70 ft³	1.05 ft³	1.40 ft³	1.75 ft³
10″	0.55	1.09 ft³	1.64 ft³	2.18 ft³	2.73 ft³
12″	0.79	1.57 ft³	2.36 ft³	3.14 ft³	3.93 ft³
14″	1.07	2.14 ft³	3.21 ft³	4.28 ft³	5.35 ft³
16″	1.40	2.79 ft³	4.19 ft³	5.59 ft³	6.98 ft³
18″	1.77	3.53 ft³	5.30 ft³	7.07 ft³	8.84 ft³
24″	3.14	6.28 ft³	9.42 ft³	12.57 ft³	15.71 ft³

80 lb bags per sonotube

Bag counts assume an 80 lb bag yields about 0.60 ft³ and are rounded up to whole bags. Buy a few spare — bags are cheaper than a second trip.

Tube diameter	24″ deep	36″ deep	48″ deep	60″ deep
6″	1	1	2	2
8″	2	2	3	3
10″	2	3	4	5
12″	3	4	6	7
14″	4	6	8	9
16″	5	7	10	12
18″	6	9	12	15
24″	11	16	21	27

ft³ per tube = π × (diameter in ÷ 24)² × (depth in ÷ 12)
80 lb bags = ft³ ÷ 0.60, rounded up · yd³ = ft³ ÷ 27

Two things the chart can’t tell you

Diameter is a structural choice, not a preference. The tube size comes from the post load and the soil’s bearing capacity, set by your deck plan or local deck code — not from what looks sturdy. See the footing size chart for the code principles.

Depth is set by frost, not by the chart. Every pier must bear below the local frost line, which ranges from near zero to 4 feet or more. Read how deep footings need to be before you cut tubes, and count posts with how many footings a deck needs.

Pouring more than a few tubes? Run your exact sizes and count through the deck footing calculator for the whole-project volume and bag total.

Sonotube Size Chart

Concrete per sonotube (cubic feet)

80 lb bags per sonotube

Two things the chart can’t tell you

Doing whole plans, not single runs?

Sonotube questions, answered.