Free estimate — verify against local code before building
Sonotube / Concrete Column Calculator
Enter tube diameter, fill depth, and quantity to get volume and whole concrete bags.
What this calculator includes
Estimate concrete for solid round form tubes, deck piers, and columns from the inside diameter, fill depth, and number of identical tubes. The result includes volume, whole bags, dry bag weight, and optional material cost.
How to use this sonotube concrete calculator
- 01
Confirm the form diameter
Enter the tube's inside diameter, because that is the space filled by concrete.
- 02
Measure concrete depth
Use the actual planned fill depth; do not include a gravel base or unfilled tube above grade.
- 03
Count identical tubes
Enter the number with the same diameter and depth. Calculate other sizes separately.
- 04
Verify bag yield
Choose a bag size, check the yield on its label, add an allowance, and round up to whole bags.
Worked example
Example: four 12 in × 4 ft tubes
Four 12 in diameter tubes filled 4 ft deep contain 12.57 ft³. With 10% waste, the order is 13.82 ft³, which rounds to 24 of the 80 lb bags at 0.60 ft³ each.
Practical buying and overage guidance
Form-tube nominal sizes and actual inside dimensions can vary. Confirm the form and concrete bag labels, brace forms against movement, and plan how each batch will be mixed and placed without cold joints.
Continue the project
Pour a Concrete Slab
Plan slab excavation, base, concrete yards or bags, forms, reinforcement allowances, delivery, labor, equipment, and contractor pricing.
Open the project workflow →Calculation sources and review
Primary references and formula assumptions are linked so you can verify them against the selected product, supplier, and adopted local requirements.
Internal formula review completed July 13, 2026. What this review covers
- Sonoco Sonotube Builder's Tube (opens in a new tab)
Manufacturer information for disposable cylindrical concrete forms.
- QUIKRETE Concrete Mix product data (opens in a new tab)
Planning yields for common concrete bag sizes.
Frequently asked questions
How is concrete volume for a Sonotube calculated?
The tube is treated as a solid cylinder: pi times radius squared times fill depth. That volume is multiplied by the number of tubes and the waste allowance.
Do I use the inside or outside tube diameter?
Use the inside diameter or the manufacturer's nominal concrete diameter. Wall thickness should not be counted as concrete.
Does this subtract the post or rebar inside the tube?
No. Posts and reinforcement usually displace little volume relative to field variation, so the estimator treats the column as solid concrete.
Can this calculator choose my pier diameter and depth?
No. Those depend on loads, soil, lateral requirements, frost depth, uplift, and local rules. Use approved plans or qualified professional guidance.
Why is bag yield editable?
Concrete mix yield varies by product and bag weight. The manufacturer's label for the exact bag is the controlling purchase assumption.