Sonotube Concrete Calculator
Bags per tube for deck footings and round forms — any diameter, any depth.
Your tubes
Materials list
Generated by AllUnits.io — allunits.io/calculators/sonotube
How this calculator figures it
Each tube is a cylinder: π × radius² × depth, plus 10% waste. Bag counts use Quikrete TDS #1101 yields (0.60 cu ft per 80 lb bag). Footing diameter and depth are structural decisions governed by soil, load, and frost line — this tool sizes the concrete order, not the footing.
How it works
Worked example — six 10" tubes, 48" deep: each holds π × (5/12 ft)² × 4 ft = 2.18 cu ft. Six tubes plus 10% waste is 14.4 cu ft — 24 bags at 80 lb, four per tube.
Bags per foot of depth (reference)
| Tube diameter | Volume per ft | 80 lb bags/ft | 60 lb bags/ft | 50 lb bags/ft |
|---|---|---|---|---|
| 8" | 0.35 cu ft | 0.58 | 0.78 | 0.93 |
| 10" | 0.55 cu ft | 0.91 | 1.21 | 1.45 |
| 12" | 0.79 cu ft | 1.31 | 1.75 | 2.09 |
Straight tube volume from the same Quikrete yields, without waste — multiply by depth in feet and round up to whole bags.
Sonotube FAQs
What size tube for a deck post?
10 to 12 inches is common for residential deck footings, but footing size is a structural decision — check your local code and permit.
How deep should the tube go?
Below the frost line; the required depth varies by region — your building department has the local figure.
Do I include the flared or bell base?
Not in this calculator — if you use a flared footing form, add its listed volume from the manufacturer to the total.
How many bags fill a 10 inch tube 4 feet deep?
About four 80 lb bags including 10% waste — the tube itself holds 2.18 cubic feet.
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Related calculators & sources
Pouring a slab as well? Use the Concrete Slab Calculator. Setting fence posts: Fence Post Concrete Calculator. Boarding the deck those footings carry: Deck Board Calculator. Bag yields come from Quikrete product data; convert measurements with the volume and area converters.
Estimates for planning and purchasing. Not engineering or code-compliance advice — confirm structural work with your local building department.