What this is
ConcreteCalc is a free concrete calculator published in nine regional versions (United States, United Kingdom, Australia, France, Germany, Poland, Spain, Italy and the Netherlands). Each version is written for its market: local bag sizes, units, currency, building standards and prices.
How the numbers are produced
Volumes use the plain geometric formulas, which are printed on the result board for every calculation so that nothing is hidden. Post holes subtract the post; stairs are computed as stacked blocks. Bag counts use a dry-mix ratio of 2,150 kg per cubic metre of placed concrete (133 lb per cubic foot), which is what the Quikrete, Sakrete, Blue Circle, Boral and European manufacturers' data sheets imply once you divide bag weight by the stated yield. Weight uses 2,400 kg/m³ (150 lb/ft³), the Portland Cement Association's value for normal-weight concrete. Mix quantities use the common 350 kg/m³ cement dosage.
Price tables are ranges collected from supplier and retailer price lists in the month shown on each page. They are planning figures, not quotes.
Who writes it
The pages are written and maintained by the ConcreteCalc editorial team and checked against the standards listed under “References” on each page (IRC and ACI in the US, BS 8500 in the UK, AS 2870 in Australia, DTU 13.3 and NF EN 206 in France, DIN EN 206 in Germany, and the national EN 206 adoptions elsewhere). We are not engineers and the site does not replace one: footings, retaining walls and anything that carries a building need a design by a licensed professional.
Corrections
If a yield, a standard or a price on any page is out of date, write to us via the contact page with the source, and we will fix it and note the change on the page.