Finding a concrete calculator on the net is not difficult. They give the DIY concretor easy access to slab calculations, which must be done before pouring a concrete slab.
Trouble is they don't help with footing calculations. In fact they seem to assume you don't have footings!! A halfway decent concrete slab calculator will calculate the concrete required for a house slab and the footings. To do this, the job must be divided into components. See the graphic below.
This concrete calculator is a sort of calculus that you may have dabbled in at school, only easier. You will need a calculator and a pad to write the initial measurements. There are four steps to this process. Each step requires a result that must be written down, then the four results added. For a concrete yardage calculator, just swap the metre amounts for yard amounts...too easy.
Tip Before you start, do a rough estimate so can compare, e.g. if the top slab will be 14m x 7m x 200mm + footings = 19.6 cubic metres + a few more metres. For your information...a truck load is between 5-7 cubic metres. That's about 5 trucks, at $2-300/cubic metre(au). Ok lets begin the maths.
Calculate the volume of the top slab (component 1) length x width x height
Calculate the volume of the square footings (components 2+5) length x width x height x 2
Calculate the volume of the footing triangle forms (components 3+4)length x width x height - there are two and they are approx. half a square each so together they are a square!
Now add the forward and rear footings (components 6, 7 and 8) x2. Same again-length x width x height, with the width (components 9 and 10). Remember the triangles are half of a square.
Ok, so we have a result. If you speak to the concrete merchant he will advise an 'overage' amount to be added in case of under-calculation. Always overestimate as the cost of the truck coming back with a small amount is high. Our next page is a guide to pouring concrete .
Have a look at my concrete slab pictorial here
Or you can go back from Concrete calculator to Concrete Footing Design
Or go to Kithomebasics home page