Sonotube Concrete Calculator
A 12-inch sonotube that is 4 feet deep holds about 3.14 cubic feet of concrete. Use this sonotube concrete calculator to estimate cylindrical footing volume, total cubic yards, and bag counts for 40, 50, 60, or 80 lb mixes before you pour deck piers, porch supports, or fence post footings.
Quick answer
Each hole is treated as a true cylinder using pi times radius squared times depth.
What this tells you
- •Each hole is treated as a true cylinder using pi times radius squared times depth.
- •Tube diameter in inches is converted to feet before the volume math runs.
- •Bag counts round up, so you can compare common bag sizes without running short mid-pour.
How to Use
- 1Enter the sonotube diameter in inches.
- 2Enter the hole depth in feet for the concrete-filled section.
- 3Set the number of holes or piers.
- 4Choose the bag size you plan to buy.
- 5Add a waste allowance if you want extra for spillage and uneven holes, then calculate.
How It Works
Formula
Per Hole Volume (cu ft) = pi x (Diameter(ft) / 2)^2 x Depth(ft)
Total Volume = Per Hole Volume x Hole Count
Total With Waste = Total Volume x (1 + Waste%)
Bags Needed = ceil(Total With Waste / Bag Yield)The calculator keeps the cylinder math exact until the final display step. Bag counts use the full unrounded volume with waste and divide by the selected bag yield, then round up to the next whole bag.
Calculation note: values are processed in the order shown above, using the current input units.
Worked Examples
Six deck footings, 12-inch tubes, 4 feet deep
That footing layout is just under 0.77 cubic yards after waste. If you switch to 80 lb bags, the same pour needs 35 bags.
Two porch piers, 18-inch tubes, 3 feet deep
This is about 0.41 cubic yards. A larger diameter tube drives volume up fast, so double-check the hole size before you buy bags.
Concrete per 4-Foot Sonotube Hole
Approximate volume and 80 lb bag count for one straight cylindrical hole before waste.
| Tube Diameter | Depth | Volume per Hole | 80 lb Bags |
|---|---|---|---|
| 8 in | 4 ft | 1.40 cu ft | 3 |
| 10 in | 4 ft | 2.18 cu ft | 4 |
| 12 in | 4 ft | 3.14 cu ft | 6 |
| 16 in | 4 ft | 5.59 cu ft | 10 |
Bag counts are rounded up and based on a nominal 0.60 cubic foot yield for each 80 lb bag.
When This Sonotube Estimate Runs Short
This calculator is built for straight cylindrical pours, which is common when a full-length sonotube lines the footing hole for a deck or porch. For that setup, diameter and depth give you a clean concrete estimate that is easy to shop against bag prices or a small ready-mix order.
Real footings are not always perfect cylinders. A bell-shaped base, loose soil at the bottom, stacked tube sections, rebar cages, or a thickened pad under the tube all change the final volume. If your footing detail widens below the tube, add that extra concrete separately.
Common mistakes
- Entering the radius instead of the full tube diameter
- Using total hole depth when the concrete will not fill the entire hole
- Skipping the number of holes on a multi-pier deck
- Comparing bag counts without checking the bag yield printed on the mix you plan to buy
Embed this calculator on your site
Drop this single line where you want the calculator to appear. It is responsive, mobile-friendly, resizes automatically, and is free to use with attribution.
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