Greenpepper's Concrete Calculator

Comes in Two Varieties:

Imperial         Metric

                  UK: Imperial                                                   Australia: Metric                                                                   USA: Imperial               

 These Calculator Pages are meant mainly for the Home Small Batch Concreter - the guy doing a job at home maybe for the first time and not sure about quantities or methods.

Pouring concrete, working with concrete, is very satisfying, it is good work. And it looks very simple: mix up the few ingredients and pour it, job done. There's more to it than that. Much, much more.As you pretty soon begin to realise when you start out on your first job.  So all the help and clarity you can get the better.  That's why these pages. Hopefully they'll help with at least part of the job: the quantities and perhaps pricing.

The main points of the method of calculation are these:

For Unit quantity of Concrete it is assumed 1.6 Units of Dry Materials will be required.
A 20kg bag of cement is assumed to have a volume of 0.01333 cu m.
A water/cement ratio of 1:2 is used and arrived at by taking 0.75 of the cement volume. This mix should be able to reach 20MPa

It should be remembered that cement density can vary between 830 kg/m3 and 1650 kg/m3 - see the Portland Cement Association page.
Hence it is sold by weight. But we are to use it by volume in our calculations.  So there's almost a built-in inaccuracy there especially when working  
with quantities smaller than one bag.

Now I've been as careful as I can and I've checked and checked and I use this calculator myself and work from it.: I think it is all good, the calcs are correct and in support of that idea I've had no comments contradicting it yet from anywhere.

But nowadays we must be careful about what we offer so I have to print this caveat here, explaining just what the situation is and disclaiming all responsibility for any use you may put this information to.

  Use At Your Own Risk.  These pages have been put together by a guy who is not a professional builder, engineer, concretor or any other kind of tradesman. They may contain errors. The calculators may give wrong results. The author accepts no responsibility whatsoever for any harm or cost incurred  by using the opinions and figures expressed here.  I can't.  You must  make your own decisions and your own choices. Be warned. Be careful. Think for yourself. Get second opinions. Check.

Note: it currently calculates ONLY the basic 1:2:3 mix for a  mix that should have a strength of at least 20MPa.

 Please email with any concerns: reports of inaccuracy, suggestions for improvement, requests for information or whatever.