How to use it
- Enter the inside diameter (12 in).
- Input the depth in feet.
- Specify how many tubes you are filling.
- Read the cubic‑yard, bag, and cubic‑foot results.
What it does – Enter the tube's inside diameter (12 in), the depth in feet, and how many tubes you plan to pour. The tool instantly converts those dimensions to total cubic feet, then to cubic yards (the unit most suppliers quote), and finally to the number of 80‑lb bags, using the fact that each bag yields about 0.6 ft³.
Why it matters – Knowing cubic yards prevents over‑ordering and costly truckloads, while bag counts help you budget material purchases.
Reading the results – Cubic feet shows the raw volume, cubic yards is the delivery volume, and bag count tells you how many mix bags to order. Adjust for waste by adding a few percent. The calculator works in real time, so you can experiment with different depths or quantities without leaving the page.
Pro tips
- Add 5‑10% extra for spillage and uneven subgrade.
- Round bag count up to the nearest whole bag; you can’t buy a fraction.
- Order concrete in cubic yards for larger jobs to reduce bag handling.
- Double‑check the tube depth; a common mistake is entering inches instead of feet.
Real-life examples
- Homeowner installing a 12‑inch fence post footing needs exact bag count.
- Contractor pouring multiple sonotube piers for a deck wants total material estimate.
- Landscaper filling decorative concrete columns asks for cubic yard total for delivery.
Case study
Mike needed 8‑foot deep footings for six 12‑inch sonotubes. Using the calculator he saw he required 2.9 cubic yards, which translated to 8 bags. He ordered exactly that amount, avoided a $150 over‑order, and finished on schedule.