How much concrete for 9 deck footings (12 inch tubes, 4 ft)?

Data checked October 2026

Short answer

9 × 12 in Sonotubes 4 ft long need 28.3 cu ft of concrete — 52 × 80-lb bags with 10% extra.

A 12 in tube holds 0.785 cu ft per foot: π × (12 ÷ 24 ft)² = 0.785; × 4 ft = 3.14 cu ft.
Quik-Tube's data sheet lists 6 × 80-lb or 7 × 60-lb; Sonoco's table lists 6 × 80-lb or 8 × 60-lb per 4 ft tube — our 6 / 7 come from the same geometry.
For 9 columns with 10% extra: 52 × 80-lb bags (4,160 lb), about $308.
Dig a 24 in hole (twice the tube) and buy 9 × 4 ft tubes.
Nine 12 in piers in a 3 × 3 grid carry a 16×16 deck.

Adjust it to your exact job

Tube size

Diameter

Sonotube sizes include 6, 8, 10, 12, 14, 16, 18, 24 in; Quik-Tube comes in 8, 10 and 12 in.

Exact diameter

= 1'

How many?

Concrete heightwhole tube

= 4' · 1.22 m

Above groundpart of it

= 6"

Footing under the tube

Pour a footing first

Quik-Tube method: 2 in of gravel, a 4–6 in footing as wide as the hole (2× the tube), then set the tube on it.

You need

52× 80-lb bags

5.2 bags per column · 1.15 yd³ including 10% extra · 4,160 lb

Per column: 3.14 ft³0.785 ft³ per foot of tube
Total concrete: 1.05yd³before waste
Hole to dig: 24in2× the tube diameter (Quik-Tube)
Bottom below grade: 3' 6"compare with your frost depth

Check against the tube makers

Bags per column, whole bags, no waste
Per column	60-lb	80-lb
This calculator (geometry)	7	6
Quik-Tube data sheet	7	6
Sonoco Sonotube table	8	6

All bag sizes for the job

Bags needed by size
Bag	Bags	Est. cost
40 lb · 0.3 ft³	104	—
50 lb · 0.375 ft³	83	—
60 lb · 0.45 ft³	70	$340
80 lb · 0.6 ft³	52	$308

Bags or a ready-mix truck?

52 bags

$308

Cheaper ✓ · materials only, before tax

1.25 yd³ delivered

$528

incl. short-load & delivery fees

At these prices a truck becomes cheaper from about 3.25 yd³ (147 bags). Over 1–2 yd³, a truck also saves hours of mixing: plan on 3–4 minutes per bag in a mixer.

That's 2.1 tons of bags — more than most pickups can carry in one trip. Ask about store delivery.

Footing depth

Deck and porch footings must sit at least 12 in below undisturbed ground (IRC R507.3.2 / R403.1.4) and below your local frost depth. Builder's-grade tubes stay in place — Sonoco notes they are not designed to be stripped.

Timeline for standard 4000 psi mix

Walk on: 24 hours
Light loads / posts: 24 hours
Keep moist (cure): 5 days ≥70°F · 7 days at 50–70°F
Protect from freezing: 48 hours

Shopping list

52 bags Standard 4000 psi mix — 80-lb bags$308
9 tubes 12 in form tube, 4 ft
9 pcs Post bases or anchor bolts, set in the wet concrete
59 gal Clean water for mixing39–59 gal; start low, never exceed the max

Estimated total$308

Cost estimate

Tap a price to use your store's

80-lb Standard 4000 psi mix
52 bags × $Pallet price applied (42+ bags)
$308

Materials total$308

Typical U.S. big-box prices checked 2026. Tap any price to enter your store's.

Did this answer your question?

Compare

12 in tubes (× 9) at other lengths

Length	Cu ft per tube	80-lb per tube	60-lb per tube	80-lb for 9 (+10%)
2 ft	1.57	3	4	26
3 ft	2.36	4	6	39
4 ft ←	3.14	6	7	52
5 ft	3.93	7	9	65
6 ft	4.71	8	11	78
8 ft	6.28	11	14	104

How this was worked out

Round forms are cylinders: area = π × radius². A 12 in tube has a 6 in radius, so π × 6² = 113.1 sq in ÷ 144 = 0.785 sq ft. Multiply by the length in feet for cubic feet.

3.14 cu ft ÷ 0.6 cu ft per 80-lb bag = 5.24, and ÷ 0.45 per 60-lb bag = 6.98. Tube tables round each tube up — here that leaves most of a bag over, so on several tubes round the total instead.

At 1.15 yd³ with waste, ready-mix (about $528 for 1.25 yd³ with fees) still costs more than bags — and a chute fills tubes in minutes.

The full method, material data and tips are on the main sonotube & column concrete calculator page.

Similar jobs

Other sizes people check

Sources

Data behind this answer

Quikrete QUIK-TUBE Building Form No. 6922 — technical data sheet — Table 1 bags per 1–4 ft of 6/8/10/12 in tube; hole 2× tube diameter; 2 in gravel and a 4–6 in footing; brace at 2 ft above grade; up to 3 ft above grade · checked October 2026
Sonoco Sonotube Builder's Tube — bags per 4 ft: 8 in 4×60/3×80, 10 in 5/4, 12 in 8/6, 16 in 13/10; below grade and up to 3 ft above · checked October 2026
Home Depot Sakrete 48 in form tubes — price history (Glassit) — 8 in × 48 in $10.88, 10 in × 48 in $14.48 (Jul 13, 2026, one tracked store) · checked October 2026
Quikrete Concrete Mix No. 1101 — technical data sheet — bag yields (80 lb = 0.60 cu ft, 60 lb = 0.45, 50 lb = 0.375, 40 lb = 0.30), water per bag, curing times; post method: 6 in of dry mix in the hole bottom, 24 h before strain · checked October 2026
Home Depot & Lowe's listings — Quikrete 80 lb Concrete Mix — $5.98–$6.98 per 80-lb bag; $5.93 bulk tier at 42+ bags; 42 bags per pallet; Fast-Setting 50 lb $7.97 · checked October 2026
Published 2026 ready-mix plant price sheets (e.g. Gehring Concrete) — $146–$285 per yd³ before fees; short-load fees $50–$200 · checked October 2026
International Residential Code 2021 — R403.1 footings & Table R403.1(1) — 12 × 6 in minimum footing, width by soil bearing, 12 in below undisturbed ground, 3 in cover over bars cast against earth; deck footings R507.3 · checked October 2026

Short answer

9 × 12 in Sonotubes 4 ft long need 28.3 cu ft of concrete — 52 × 80-lb bags with 10% extra.

A 12 in tube holds 0.785 cu ft per foot: π × (12 ÷ 24 ft)² = 0.785; × 4 ft = 3.14 cu ft.

Quik-Tube's data sheet lists 6 × 80-lb or 7 × 60-lb; Sonoco's table lists 6 × 80-lb or 8 × 60-lb per 4 ft tube — our 6 / 7 come from the same geometry.

For 9 columns with 10% extra: 52 × 80-lb bags (4,160 lb), about $308.

Dig a 24 in hole (twice the tube) and buy 9 × 4 ft tubes.

Nine 12 in piers in a 3 × 3 grid carry a 16×16 deck.