how much ballast and cement do i need

Hi its worth going on the internet and working it out with the online calculators which are available, these are very good and they will give you the correct amount if you wish to mix it yourself, its also worth considering that you can have this ready mixed and delivered which saves on labour time and labour costs ,ready mixed your looking at 0,81m cubed so order a cube this is basically the minimum and this will make it easier, quicker and cleaner rough cost £150 and a couple of barrows and a mate, at a depth of 150 mm i would place some re-bar in it just for some extra strength, also it would be worth cutting a line through the concrete half way to minimize the chance of cracking.

You will need 1.75 tonne ballast and 5 bags of cement if you are doing a 3:1 ratio mix. Hope this is of help.