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.

- Component 1 is the top slab
- Components 2 and 5 are the side footings
- Components 3 and 4 are the triangle form footings
- Component 7 is the front and rear footings
- Components 6 and 8 are the triangle forms for the front and rear footings
- Components 9 and 10 are the widths (cross section) of the front and rear component 7

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.

**Step one**

Calculate the volume of the top slab (component 1) length x width x height

plus

**Step two**

Calculate the volume of the square footings (components 2+5) length x width x height x 2

plus

**Step three**

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!

plus

**Step four**

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