Rex says
Everyday utility math — the kind you'd otherwise pull up four browser tabs for. I keep it to one clean answer.
Try a scenario
Click to load — tweak from there.Inputs
Result
Ready-mix needed
0.46
cu yd
Equivalent 80lb bags
21
Volume per pier
1.91
cu ft
Total cubic feet
12.4
Psst — share this and help Rex grow
One click, a permanent link with your numbers baked in.
How to use this
- 1Enter tube diameter (in).
- 2Enter pour depth (in).
- 3Enter number of piers.
- 4Enter waste factor (%).
- 5Read your ready-mix needed on the right — it updates as you type.
- 6Hit Share to keep the scenario or send it to someone.
About this calculator
Sonotube (cardboard cylinder) forms are the standard way to pour round concrete footings under deck posts, porches, and pergolas, and because the form is a perfect cylinder the math is straightforward once you know tube diameter and pour depth. This calculator takes tube diameter and depth, computes cylindrical volume in cubic feet using π×r²×depth, multiplies by your pier count, then converts to both cubic yards for ready-mix ordering and 80lb bags for hand-mixing, since most sonotube jobs (6-12 piers) sit right at the boundary between the two approaches. Common deck footing tubes run 8, 10, or 12 inches in diameter depending on local frost depth code and the load path from beams above, and depth is usually set to your area's frost line, often 36-48 inches in cold climates. A waste factor is included since tubes are rarely trimmed to an exact depth and a little overpour above grade is normal for crowning the top of the footing.
Worked example
Using the values the calculator loads with:
Inputs
- Tube diameter: 10 in
- Pour depth: 42 in
- Number of piers: 6
- Waste factor: 8 %
Results
- Ready-mix needed: 0.46
- Equivalent 80lb bags: 21
- Volume per pier: 1.91
- Total cubic feet: 12.4
What each field means
Inputs
- Tube diameter (in)
- The tube diameter used in the calculation, measured in in. Starts at 10 in so you have a working example on load. Accepted range: 6–24 in.
- Pour depth (in)
- The pour depth used in the calculation, measured in in. Starts at 42 in so you have a working example on load. Accepted range: 6–72 in.
- Number of piers
- The number of piers used in the calculation. Starts at 6 so you have a working example on load. Accepted range: 1–60.
- Waste factor (%)
- The waste factor used in the calculation, measured in %. Starts at 8 % so you have a working example on load. Accepted range: 0–25 %.
Results
- Ready-mix needed
- cu yd
- Equivalent 80lb bags
- Returned as a whole number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Volume per pier
- cu ft
- Total cubic feet
- Returned as a decimal number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
FAQ
How deep should sonotube footings be poured?
Deep enough to sit below your local frost line — often 36-48 inches in northern climates and as little as 12 inches in frost-free southern regions — always check local building code since frost heave can crack footings poured too shallow.
What diameter tube do I need for a deck post?
8-10 inches is common for typical residential deck posts; larger structures or beam spans requiring higher point loads may call for 12+ inch tubes per an engineer's or code table's load requirements.
Is it cheaper to hand-mix bags or order ready-mix for sonotube piers?
Under about 8-10 piers, bagged mix is usually more practical since a ready-mix truck minimum often exceeds what a handful of tube footings need; beyond that, a small ready-mix order or short-load delivery starts to pay off.
Do I need rebar in sonotube piers?
Most codes require a vertical rebar cage or post anchor embedded in the footing for structural connections; check local code, but adding rebar is cheap insurance regardless of the minimum requirement.
Accuracy and limitations
- Estimates assume standard, average conditions — local rules, pricing, and materials vary.
- Results are rounded for readability; add a buffer before ordering, booking, or committing.
- Double-check anything with a real cost attached against a local quote.
Related tools
Cite this calculator
Writing about this topic? Grab a citation — every link helps keep these tools free.
RevenueLab. (2026). Sonotube Concrete Piers Calculator. Retrieved from https://www.revenuelab.fyi/toolbox/concrete-sonotube-piers-calculator
<p>Source: <a href="https://www.revenuelab.fyi/toolbox/concrete-sonotube-piers-calculator" target="_blank" rel="noopener">Sonotube Concrete Piers Calculator — RevenueLab</a> (2026).</p>
Source: [Sonotube Concrete Piers Calculator — RevenueLab](https://www.revenuelab.fyi/toolbox/concrete-sonotube-piers-calculator) (2026).