By using my concrete volume calculator, you will be able to determine the quantity and cost of concrete needed for your volumetric pour.If you want to develop a gut feeling for estimating quantities manually, use the concrete volume calculator formulas below and you will be able to calculate the concrete volume for your pour. Please note that these formulas apply to structures that are either circular or cylindrical(column)-shaped. Concrete volume calculations are more involved than those for a square or rectangular slab. Stick with me and all will be OK. Please review and write down, or print-out the concrete volume calculator formulas and examples. Always check your calcs twice! If you are not interested in learning to figure concrete volume manually, or you are in a rush, just download my handy concrete volume & cost calculator gadget and you'll have it to use whenever you need it. Some basic info...Concrete is calculated in cubic yards (one cubic yard = 27 cubic feet). Concrete can be be ordered in ready-mixed cubic yards or mixed on-site in 60 or 80 lb. bags, which are the most commonly used bag sizes. Concrete volume calculator formulas for circular or column-shaped structures, bag and cubic yardage:(3.14 x r (feet) x r (feet) x (T (inches) / 12)) = cubic feet of concrete (CF) Number of bags of concrete needed CF / 0.45 = number of 60 lb. bags CF / 0.6 = number of 80 lb. bags
Number of cubic yards of concrete needed: CF / 27 = cubic yards Formula Stuff: / = divided by r = radius of the circle in feet (1/2 of the diameter) T = Thickness in inches CF = Cubic feet of concrete Fixed Mathematical Values: 3.14 = pi (180 radians) 1728 = # of cubic inches in a cubic foot Example 1: Circular-Shaped Slab CalculationsA circular slab 6" thick where the circle has a radius of 6' (12' diameter circle) ((3.14 x 6' x 6') x (6" / 12")) = 56.5 cubic feet of concrete 56.5 / 0.45 = 126 (125.6) 60 lb bags of concrete 56.5 / 0.60 = 95 (94.2) 80 lb. bags of concrete 56.5 / 27 = 2.09 cubic yards of concrete (it's best to round bag quantity up to at least the next bag to be certain that enough concrete will be available) Example 2: Column-Shaped (column, footing)CalculationsA concrete column 12 feet (144 inches) high where the column has a radius of 12 inches (24 inch tube diameter) (3.14 x 12" x 12" x 144") ÷ 1728 cubic inches (trust me, the 1728 is proven) = 37.68 cubic feet of concrete ---> 37.68 cf / 0.45 cf/bag = 84 60 lb bags of concrete (buy 93 bags) ---> 37.68 / 0.60 cf/bag = 63 (it's best to always round bag quantity up by 10 percent to ensure enough concrete is available) If ordering your concrete from a pre-mix supplier: ---> 37.68 cf / 27 cf/cy = 01.4 cubic yards of concrete (I typically add 10% above the raw CY value, so I would order 1.4 CY X 1.10 = 1.54 CY of concrete from a reputable concrete supplier. I hope the above concrete volume calculator examples were helpful to you. As your projects get bigger, time is less available, and you develop the gut feel I mentioned above, it will be a smart idea to use a handy concrete volume calculator to do the calculating for you... but not until you understand the numbers it gives you. Calculators are not intuitive, but you are! New for 2010, I have created a concrete calculator that accurately calculates concrete cubic yardage, cubic meters, and bags needed. And to boot, it estimates the cost of the calculated concrete and can be saved to your desktop to use whenever you need it. If you have any questions about concrete volume calculators or need additional info., please feel free to shoot me an email. Meet-Mr-Concrete.com provides concrete construction advice at no charge and in good faith for consideration only. We do not warrant the implementation of its content and are to be held harmless when and if any advice or ideas provided are utilized. The risk from using it lies entirely with the user. 
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