Calculation details
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What does this calculator estimate?
A sonotube calculator estimates concrete for cylindrical columns and footings. Enter the tube diameter, height, number of tubes, and waste to get cubic yards and bag counts.
- Column volume = π × r² × height
- 1 cu yd = 27 cu ft
- 60 lb bag ≈ 0.45 cu ft; 80 lb bag ≈ 0.6 cu ft
How column concrete is calculated
Round columns use the cylinder volume formula: π × radius² × height. The radius comes from the tube diameter converted to feet. Multiplying by the number of tubes gives total volume, converted to cubic yards for ordering.
Limitations to watch for
The estimate assumes straight cylindrical tubes filled to the top. Bell footings, flared bases, and stepped columns need additional volume. Ready-mix and bagged concrete yields vary slightly by mix. Rebar and tube waste are not included.
How to use it in practice
Measure the tube diameter and pour height in feet (convert inches ÷ 12). Count all columns of the same size. Add 10% waste. Use the bag count for small jobs or the cubic yards for a ready-mix order.
['Enter the tube diameter in inches.', 'Enter the pour height in feet and the number of tubes.', 'Enter waste %; the tool computes cubic yards and bag counts.']
How column concrete is calculated
Concrete volume for a cylindrical column is π × radius² × height. A 12-inch-diameter, 4-foot column: 3.1416 × 0.5² × 4 = about 3.14 cubic feet ≈ 0.116 cubic yards. The calculator converts diameter, height, and count into bags of concrete mix.
The bag count depends on mix
A 60-pound bag of standard concrete mix yields about 0.45 cubic feet; an 80-pound bag yields about 0.6 cubic feet. The calculator applies the bag size so the shopping list matches what you will actually carry home.
Footings and below-grade depth
The sonotube extends below grade to a footing or to frost depth. Include the full buried length in the height input — the below-grade concrete is part of the pour. A 4-foot exposed column on a 2-foot buried tube is a 6-foot column for volume purposes.
Oversize and waste
Bags never pour perfectly and tubes flare slightly at the bottom; adding 10 percent covers spill, over-dig, and the flare. On a 20-column deck, the difference is several bags.
A worked example
Ten 12-inch-diameter, 4-foot columns: each is about 3.14 cu ft, total 31.4 cu ft — about 70 sixty-pound bags or 53 eighty-pound bags. The calculator runs the total so one trip to the store is enough.
How this calculator works
Formula
Radius r = (diameter ÷ 2) ÷ 12 (ft). Volume per tube = π × r² × height. Total = volume per tube × number of tubes. Cubic yards = total ÷ 27. Order = cubic yards × (1 + waste%). Bags: 60 lb ≈ 0.45 cu ft each; 80 lb ≈ 0.6 cu ft.
Worked example
Four 12 in diameter × 4 ft columns: r = 0.5 ft, volume per tube ≈ 3.14 cu ft, total ≈ 12.57 cu ft ≈ 0.465 cu yd. With 10% waste: ≈ 0.51 cu yd, or about 31 sixty-pound bags.
Assumptions to verify
- Tubes are uniform cylinders filled to the top.
- Bags are 60 lb (0.45 cu ft) or 80 lb (0.6 cu ft).
- Waste covers spillage and uneven tops.
Frequently asked questions
How much concrete is in a sonotube?
Use the cylinder formula: π × radius² × height. A 12 in diameter × 4 ft tube holds about 3.14 cu ft.
What is a sonotube?
A brand of cylindrical cardboard form used to pour round concrete columns, footings, and piers.
How do I convert diameter to radius in feet?
Divide the diameter by 2 to get the radius in inches, then divide by 12: 12 in diameter → 0.5 ft radius.
How many bags of concrete do I need per column?
Divide the volume by the bag yield: a 60 lb bag makes about 0.45 cu ft, an 80 lb bag about 0.6 cu ft. Four 12×4 ft columns need about 31 sixty-pound bags with waste.
Should I order ready-mix or bags?
Bags work for small jobs and tight access; ready-mix is better for volume. Compare cost and delivery minimums.
Does this include rebar?
No — rebar or reinforcement is planned separately based on the structural requirements.
What if my column flares at the base?
A bell footing adds significant volume. Calculate the footing separately and add it to the column volume.
How much concrete for a sonotube?
π × radius² × height per column; convert cubic feet to bags using the mix yield.
How many bags of concrete per tube?
A 12×4-ft tube ≈ 3.14 cu ft — about 7 sixty-pound bags.
Do I include the buried portion?
Yes — the tube below grade is part of the pour and the volume.
How much extra should I buy?
About 10% for spill, flare, and over-dig.
Cite this tool
BoringToolsKit. “Sonotube Concrete Calculator.” boringtoolskit.com/sonotube-concrete-column/ (reviewed 2026-08-25). Free to reference in articles, syllabi, and answer posts with a link.
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