I'm looking for either an online calculator or the formulas to calculate how much concrete I need I'm pouring footings 24"x24" at 8" thick. I'm also pouring 8" piers that will be around 7' (max I hope) and I need to figure out how much concrete to get. how much water per 80lb bag should I figure on? We'll be hauling the water. does anyone know where I can find sonotubes that long? I've found them only in 4' lengths locally.

Footings 2â (length) x 2â (width) x 0.67â (depth) = 2.67 cubic feet Piers 0.33â (radius) x 0.33â radius x 3.14 (pi) x 7â length = 2.39 cubic feet One 80 pound bag of Sakrete Contractors mix yields 0.60 cubic feet of concrete. You'll need about 8.5 bags of Sacrete for each footing/pier combination.

Here are two recent threads on the shop talk board: Concrete calculators: http://homesteadingtoday.com/showthread.php?t=90380 costs of concrete: http://homesteadingtoday.com/showthread.php?t=90389 I also read somewhere around these boards that there is a compression factor when converting dry cubic yards to wet, regarding compacting out the air space in the sand. I think s/he said something like you will need approx. 11% more than actual finished size. That's a new concept for me, but I've never done flatwork, either.

Pre-mixed Concrete is sold by the cubic yard and a truck will usually hold up to 13 yards. Cubic yard = 3' by3' by 3' = 27 cubic ' 1 Cubic ' = 1728 cubic " (12x12x12) Your footings 24"x24" at 8" thick. =4608 cu" or 2.66 cu' You didn't say how many you were pouring. Google has an on-line calculator for this. I'm also pouring 8" piers that will be around 7' (max I hope) and I need to figure out how much concrete to get. The volume of a cylinder equals the (area of the base)*height = π r2 h Pi times the radius squared(in other words the area of the base) times the height So, 3.12 * 16 (radius is 1/2 diameter, square it)* 96"=4792 cu" or 2.77 cu' each. You may find in considerably cheaper and easier to order the concrete pre-mixed than to buy the bags and mix your own. Sand cost at $20/ton Premixed contrete here was $54.00/yard. Don't take any crap off the delivery guy about how he has to get back. Just tell the concrete company this is going to be a slow pour and they will stay there all day, if they have to. By the way, for about $8.00/yard you can have them add a retardent that keeps the concrete from setting up too fast. Takes about 24 hours to set up with that added. how much water per 80lb bag should I figure on? We'll be hauling the water. does anyone know where I can find sonotubes that long? I've found them only in 4' lengths locally.