Sonotube Calculator
A tube form (Sonotube is Sonoco's brand name; QUIKRETE sells QUIK-Tube) turns each footing into a cylinder, so the concrete is π × radius² × depth. Pick the tube diameter, how deep you'll fill it and how many piers you have, then the bag size you'll buy. The calculator returns the concrete per tube, the bags for one tube and for the whole job, cubic yards if you're ordering a truck, and the 4 ft tubes to buy.
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Worked example: six 10 in piers, 4 ft deep
| Step | Working | Result |
|---|---|---|
| Radius | 10 in ÷ 2 = 5 in = 0.417 ft | 0.417 ft |
| One tube | π × 0.417² × 4 | 2.18 cu ft |
| Six tubes + 5% | 2.18 × 6 × 1.05 | 13.74 cu ft |
| 80 lb bags | 13.74 ÷ 0.60, rounded up | 23 bags |
| Tubes to buy | one 4 ft tube per pier | 6 |
Concrete per foot of tube
| Diameter | Cu ft per ft | 80 lb bags per 4 ft tube | 60 lb bags per 4 ft tube |
|---|---|---|---|
| 6 in | 0.2 | 2 | 2 |
| 8 in | 0.35 | 3 | 4 |
| 10 in | 0.55 | 4 | 5 |
| 12 in | 0.79 | 6 | 7 |
| 14 in | 1.07 | 8 | 10 |
| 16 in | 1.4 | 10 | 13 |
| 18 in | 1.77 | 12 | 16 |
| 20 in | 2.18 | 15 | 20 |
| 24 in | 3.14 | 21 | 28 |
The 6–12 in rows match QUIKRETE's QUIK-Tube capacity table exactly (for example 6 bags of 80 lb mix for a 4 ft, 12 in tube), because that table is the same sum: the tube's volume divided by the bag's yield, rounded up. Doubling the diameter quadruples the concrete: a 12 in tube holds four times what a 6 in tube does.
Before you pour
- Set the depth from your plans and the local frost depth — see the deck footing depth guide.
- Brace any tube that stands more than about 2 ft above grade, and rod the concrete to drive out air pockets.
- Set the post base or anchor while the concrete is wet.
Not sure how many piers? The deck post calculator counts them from the deck size, and the deck footing calculator sizes the footing. Pouring into plain holes without forms? Use the concrete footing bags calculator; for a floating deck on precast blocks, try the deck block calculator.
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Building something else? Try our sister calculators
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Frequently asked questions
- How much concrete is in a Sonotube?
- π × radius² × depth. A 10 in tube is 5 in (0.417 ft) in radius, so 4 ft of it holds π × 0.417² × 4 = 2.18 cu ft. A 12 in tube 4 ft deep holds 3.14 cu ft, an 8 in tube 1.40 cu ft and a 6 in tube 0.79 cu ft.
- How many bags of concrete for a 12 inch Sonotube?
- For 4 ft of a 12 in tube, six 80 lb bags or seven 60 lb bags. The tube holds 3.14 cu ft; an 80 lb bag yields about 0.60 cu ft and a 60 lb bag 0.45 cu ft. QUIKRETE's own QUIK-Tube table gives the same counts.
- How many bags for a 10 inch or 8 inch tube?
- A 4 ft, 10 in tube takes four 80 lb bags (2.18 cu ft) and a 4 ft, 8 in tube takes three (1.40 cu ft). For 3 ft, it's three bags for 10 in and two for 8 in.
- When should I order ready-mix instead of bags?
- When the job passes about a cubic yard (27 cu ft, about 45 bags of 80 lb). Twelve 12 in tubes 4 ft deep need 37.7 cu ft — 1.4 cu yd or 63 bags — which is a lot of hand mixing. Ask local suppliers for a short-load price and compare it with the bags.
- How many tubes do I need to buy?
- Tube forms usually come in 4 ft lengths. If each pier is 2 ft or less, one tube cuts into two or more forms; a 3 ft pier uses one tube and leaves a 1 ft offcut. The calculator counts whole tubes from your depth and number of piers.
