MixRatio answers one question: how much material to order. Type the dimensions of a slab, a footing, a column, a post hole, a step or a curb, and it returns the volume in cubic feet, cubic yards and cubic metres, plus the bag count at each of the 5 common bag sizes. It is meant for the person in the yard deciding what goes on the truck, not for a design office. There is no account, and the calculators run in your browser.
What the 183 guides are
179 of them are worked examples produced by a generator script: one page per common size, each running a specific slab, footing or hole through the same functions the 6 calculators call, with its inputs, volumes and bag counts laid out. They are mostly tables, because each has one job. The other 4 are explainers, one per file, covering what a ratio such as 1:2:4 means, how mortar differs from grout, and why bag counts differ between brands. Read the explainers at the top of the guide index for understanding rather than a number.
Where the numbers come from
Bag counts rest on one constant, 0.0075 cubic feet of placed concrete per pound of dry pre-mix, which gives 0.30 cubic feet from a 40 lb bag, 0.45 cubic feet from a 60 lb bag, and 0.60 cubic feet from a 80 lb bag. The 19 entries in the mix ratio reference are not computed: the data file labels its mortar types as ASTM C270 and its concrete classes as IS 456 nominal mixes or common practice, and gives grout, render and screed as trade proportions, with no per-entry citation. Ratios are by volume unless an entry says otherwise, and strengths are typical values, not design values.
Who runs it
One independent developer builds and maintains MixRatio, with no staff or office, and also publishes ThreadRef, SpanRef, CogoKit, and Irrigaudit. Guides appear under the MixRatio name with no individual byline, and their structured data gives the MixRatio organization as author. No engineer or concrete technologist is credited. Guide dates show the most recent change to each guide's words.
What a planning estimate is not
- Not a structural mix design. Anything that carries load, retains soil or holds a building up must follow your local building code and an engineer's specification. A nominal ratio from a table is not that specification.
- Order more than the number. Over-excavation, sub-grade loss, spillage and waste all push the real quantity up. Use the calculator's waste allowance.
- The printed bag wins. If the yield on your bag disagrees with ours, yours is right; ours is one planning constant across products.
- Not a test result. Cure times, strength gain and water content here are references. Cylinder breaks, slump tests and site conditions are the evidence.
- Not affiliated with anybody. ASTM and other standards bodies are named to identify where a label comes from; no relationship with them, or with any bag manufacturer, is claimed.
If a number here is wrong
If a ratio is wrong or a bag count does not match the bag in front of you, email [email protected] and quote the figure along with the page it is on. What is stored and what is promised sit in the privacy policy and the terms.