Sonotube Concrete Calculator
Plan round form-tube pours without guessing from a flat slab formula. Enter the inside diameter and actual concrete fill height for each tube.
How the calculation works
For each solid cylinder, volume in cubic feet = π × (inside diameter in feet ÷ 2)² × fill height in feet. Multiply by the number of identical tubes, then divide by 27 for cubic yards.
Worked example
Four tubes with a 12 in inside diameter and 4 ft of concrete fill need about 12.57 ft³, or 0.47 yd³ before extra. With 10% extra, plan for about 0.51 yd³ or 24 bags at 0.60 ft³ per 80 lb bag.
Before you order
Use the tube’s inside diameter, not the outside label dimension. This estimates a full, solid tube only; it does not size a footing bell or account for displaced steel. Your project plans determine depth and reinforcement.
Review the calculation method and source notes, then use the supplier checklist before placing an order.
Measuring form tubes
Use the tube’s inside diameter and the actual height that will be filled. A 12 in inside diameter is a 1 ft diameter, so a 4 ft solid fill is π × 0.5² × 4 = about 3.14 ft³ per tube. Four identical tubes need about 12.57 ft³ before allowance. If tubes have different heights, calculate each group separately.
A spread footing or enlarged bell below the tube is not part of its cylindrical volume. Calculate that additional shape separately from the tube and add it to the order. Reinforcing steel displacement is usually small for a planning estimate, but project documents control the final quantity.
Questions before you order
Can I enter the printed tube size?
Use the inside diameter that the concrete fills. Confirm the actual inside dimension if the printed nominal size differs.
Does this include a bell footing?
No. Add the bell or pad as a separate shape.
Why is the bag count rounded up?
You buy whole bags. The tool divides waste-adjusted volume by the entered finished yield, then rounds the count upward.
Continue planning
Content and calculator by pourmeasure. Formula and assumption notes: methodology and sources. Updated October 2026. No independent engineering review is claimed.