What Is the Concrete Cylinder Calculator?
This calculator estimates how much concrete you need to fill one or more cylindrical forms — such as deck footings, columns, piers, sonotubes, or post bases. Enter the diameter and height (depth) of the cylinder in inches plus how many you are pouring, and it returns the total volume in cubic yards and cubic feet, an estimated concrete weight, and the number of 60 lb bags required.
How to Use It
1. Measure the inside diameter of your tube or hole in inches.
2. Measure the height or depth the concrete will fill in inches.
3. Enter how many identical cylinders you are casting.
The tool computes total volume and rounds bag counts so you can order with confidence. It is a good idea to add 5–10% extra to cover spillage and form variation.
The Formula Explained
A cylinder's volume is the area of its circular base times its height: $$V = \pi \times \left(\frac{d}{2}\right)^2 \times h$$ With measurements in inches, the result is in cubic inches. To convert to cubic yards — the unit concrete is sold in — divide by 46,656, since one cubic yard equals \(36 \times 36 \times 36 = 46{,}656\) cubic inches. For cubic feet, divide by 1,728. We estimate weight at about 4,050 lb per cubic yard and assume a 60 lb bag yields roughly 0.45 cubic feet.
Worked Example
A sonotube column 12 inches in diameter and 48 inches tall: radius = 6 in, so $$V = \pi \times 6^2 \times 48 = \pi \times 36 \times 48 \approx 5{,}428.67 \text{ in}^3$$ Divided by 46,656 \(\approx 0.116\) cubic yards, or about 3.14 cubic feet — roughly 7 bags of 60 lb concrete mix per column.
FAQ
Why measure in inches? Small forms are easiest to measure in inches; the calculator handles the conversion to cubic yards automatically.
Should I order extra? Yes — add about 10% for waste, over-excavation, and spillage so you don't come up short mid-pour.
How accurate is the bag count? Bag yield varies by mix and water content; the 0.45 ft³ per 60 lb bag figure is a common average — always check your product's label.
