How many bags of concrete does it take to fill a 10 round sonotube 4' deep?

To fill a 10-inch diameter sonotube that is 4 feet deep, you'll need to calculate the volume of the tube. The formula for the volume of a cylinder is V = πr²h. The radius is 5 inches (0.417 feet), so the volume is approximately 0.544 cubic feet. A typical bag of concrete (60 lbs) yields about 0.45 cubic feet, meaning you'll need about 1.2 bags of concrete to fill the sonotube completely. Therefore, you should plan on purchasing 2 bags to ensure you have enough material.