# Concrete, weight/cubic metres?

Possibly a stupid question, but how many 25kg bags of ballast (with a 5:1
mix) would it take to make 1 cubic metre of concrete?
I really have no idea how to work this out myself.
A little appreciated property of the Google search engine is it's ability to answer 'plain language' queries: I typed the search string "How many 25Kg bags of ballast to make I cubic metre?" and in 0.69 seconds it responded by pointing to a Community Forum discussion about shed bases.
The message from "ARWadsworth" contains these words:
Figures I have are for a cubic yard but I am sure you will be able to work out the fiddle factor without any help from me. Tons and Tonnes are almost interchangeable.
@ 5:1 1.446 tons all-in mix and 0.231 tons of cement.
If you want to go down the equivalent 1:2:4 route that would require 0.513 tons of sand and 0.933 tons of gravel for the same amount of cement.
I have used Google as a calulator and a thesaurus before. I did not know about that search option.
My search for cubic metres etc was crap. Cheers for that info.
The density of concrete varies but is generally taken to be approximately 2400 kg per cubic metre (2.4 tonnes). If you're using a 5:1 mix then divide 2400 by 6 units and multiply by five to calculate the mass of ballast required for a cubic metre.
2400/6 = 400 400*5 = 2000kgs.
Therefore the number of 25kgs bags required would be 2000/25 = 80. I have ignored the mass of the water to be added plus the moisture already present in the ballast for simplicity.
I assume you're using 1 cubic metre as a unit volume otherwise you will need to order in bulk as the man said.
AT
Thank you Roger.
I will not be mixing a cubic metre in one go! I now have an idea how much ballast is needed for the smaller jobs I need to do. It will be bulk buying as it is much cheaper (30% cheaper)
Cheers
Pick your mix from the tables here:

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