Concrete Column & Sonotube Calculator
Enter your measurements
Extra to cover cuts, breakage, and mistakes.
Results
- Concrete needed0.13 cubic yards
- Volume3.46 cubic feet
- 60 lb bags8
- 80 lb bags6
Estimated cost
per cubic yard of ready-mix, delivered
Per cubic yard of ready-mix delivered; this is the reference price for larger pours and excludes any short-load surcharge. For the bag counts shown above, expect roughly $6–$9 per standard 80 lb bag or $5–$8 per 60 lb bag at retail, which makes bagged concrete the cost-effective default for most sonotube column projects under about a yard.
Estimate only — prices vary by region, supplier, and season. Get a local quote before buying.
This concrete calculator for sonotube forms tells you exactly how much concrete you need for round columns — deck posts, fence posts, pier footings, or any cylindrical form. Enter your tube diameter, depth, and number of columns, and the calculator returns cubic yards, cubic feet, and bag counts for both 60 lb and 80 lb bags, with an optional waste factor built in. Sonotubes (and equivalent brands like Quik-Tube) come in standard diameters from 6 inches up to 36 inches and are sold by the linear foot at most lumber yards and big-box stores. Because column pours are typically small — often a fraction of a cubic yard per pour — ready-mix delivery rarely makes economic sense, and most DIYers fill these from bags. Knowing your exact bag count before you head to the store prevents the common mistake of hauling home too little concrete mid-project, when a half-set batch in one tube can't wait for a second trip.
How it’s calculated
Volume of each tube = π × (Diameter ÷ 2)² × Height, multiplied by the number of columns, then ÷27 for cubic yards.
Worked example
For four 12-inch diameter columns each 4 feet deep with a 10% waste allowance, the calculator returns 0.51 cubic yards (13.82 cubic feet) of concrete. That works out to 31 bags of 60 lb mix or 24 bags of 80 lb mix — a heavy but manageable load that fits in most pickup beds in one trip. This is a typical deck post scenario where bag concrete makes far more practical sense than calling a ready-mix truck for half a yard.
Inputs
- Diameter
- 12 in
- Height
- 4 ft
- Number of columns
- 4
- Waste / overage
- 10 %
Result
- Concrete needed
- 0.51 cubic yards
- Volume
- 13.82 cubic feet
- 60 lb bags
- 31
- 80 lb bags
- 24
- Estimated material cost
- $72 – $95
Materials & pricing near you
Bagged concrete mix — the practical choice for most column pours — runs roughly $5–$8 for a 60 lb bag and $6–$9 for a standard 80 lb bag at national home centers as of 2026, with high-strength and fast-set formulas reaching $10–$12. Rural hardware stores and regional co-ops often charge more. Ready-mix delivered in small quantities typically carries a short-load surcharge (commonly $100–$200 or more) on top of the per-yard price, making bags the economical default for anything under about 1 yard. Sonotube forms themselves are priced per linear foot and climb steeply with diameter. In cold climates, concrete poured in tubes must reach below the local frost line — check your jurisdiction's frost depth before setting post depth, since undershooting can mean a failed inspection or posts that heave within a few winters.
Frequently asked questions
How deep should I set a Sonotube for a deck post?
Depth depends on your local frost line, which ranges from essentially zero in the deep South to 60 inches or more in northern states like Minnesota. Most jurisdictions require the bottom of the footing to sit below that line so the ground can't heave it. Your building department can give you the exact required depth, and deck footings almost always need a permit and inspection — confirm both before you dig.
Can I pour my Sonotubes one at a time, or do all columns need to be filled at once?
You can fill tubes one at a time — there's no structural reason every column has to cure simultaneously, since each column acts independently. Pouring one or two per session keeps each batch manageable when you're mixing bags by hand. If you're reusing a form, let the pour set before stripping it, though most builders leave the cardboard tube in place permanently.
Why does the calculator give bag counts instead of just cubic yards?
For column pours under roughly 1 cubic yard, bagged concrete is almost always the cheaper and easier choice. Ready-mix trucks have order minimums (often around 1 yard) plus short-load fees that make small deliveries expensive. The bag count tells you exactly what to buy — and rounding up by a bag or two is normal, since you'd rather have a little extra than run short mid-pour.
How do I measure the diameter of a form or hole for this calculator?
Measure straight across the widest point, through the center. For a hand-dug hole that isn't perfectly round, take two perpendicular measurements and average them. Sonotube inner diameters run very close to the labeled nominal size, so for volume estimating you can simply enter the printed diameter — an 8-inch tube holds essentially an 8-inch column of concrete.