Where every number on this site actually comes from.
Every number on this site comes from one of three places: the manufacturer’s data sheet for the bag I’m holding, the practice guidance from the trade body that publishes it, or what I learned the expensive way on a flip. The order of the tiers is also the order of trust.
Manufacturer spec sheets first — because the Quikrete bag tells you what’s in the bag, and the Daltile box tells you the coverage in square feet. Trade-body guidance second — because the American Concrete Institute has watched more pours than I will in a lifetime, and the TCNA waste percentages are based on decades of installation data. Lived experience third — not as the primary citation, but as the marginalia that explains why the published number doesn’t survive contact with a Saturday in July.
- 01Manufacturer data sheetsBagged products, ready-mix design specs, fastener load tables.Quikrete 80 lb concrete mix yields 0.6 ft³ per bag per the printed spec on the bag. Ozinga ready-mix is sold by the cubic yard with a published 3 yd³ minimum for residential delivery in Cook County. Daltile / MSI box coverage and waste-factor norms come from the manufacturer install guides. Numbers traceable to a printable PDF or a bag in the garage.
- 02Trade-body practice guidanceACI, NRMCA, TCNA, NDS, ICC residential code.The 4-inch residential slab thickness, the 5% waste cushion default, the deck-footing depth-by-frost-line table — sourced to ACI 332 residential concrete practice, the TCNA Handbook for tile waste percentages, IRC R403 for footings, and AWC DCA-6 for prescriptive deck framing. Citations sit inline on each calculator’s methodology drop-down.
- 03Lived experience — the expensive lessonsMarginalia, not citation. Always labelled as such.The order-cushion sizing, the bagged-vs-ready-mix inflection point around 1.5 yd³, the “don’t order short” default — these come from three Chicago-area flips and are labelled as field notes throughout the site. Read them as the operator’s opinion, not as published guidance.
- 04What is never the sourceThe provenance line we draw a hard line on.No competitor calculator outputs are reverse-engineered. No forum posts are paraphrased as fact. No Amazon product copy is used as a spec source. Pinterest landscape content is not a citation. If a number can’t be tied to a manufacturer sheet, a trade body, or a flip I personally ran, the calculator doesn’t ship the number.
Per-cluster sourcing
Sources are layered by what kind of claim they back, not flat-listed. ACI 318 is structural code, not yardage arithmetic — citing it for “how many yards do I order” reads as miscalibrated authority.
| Cluster | Geometry | Yields & coverage | Practice + waste | Code |
|---|---|---|---|---|
| Concrete | Site arithmetic (own derivation, formula shown) | Quikrete / Sakrete / SpecMix bag-yield data sheets | NRMCA + manufacturer (waste %, delivery minimums, slump) | ACI 318, IRC 2021 (only for structural concrete) |
| Topsoil | Site arithmetic | Bag-volume conventions per supplier (40 lb / 1 cu ft typical) | USDA NRCS bulletins; cooperative-extension services | — |
| Mulch | Site arithmetic | Bag conventions (2 cu ft / 3 cu ft) | Cooperative extension; ANSI A300 for depth recommendations | — |
| Tile | Site arithmetic + manufacturer box-coverage data sheets | Manufacturer waste norms (10% standard, 15% diagonal/herringbone) | Manufacturer install guides | TCNA handbook, ANSI A108 / A118 (for installation method content) |
| Deck (v1 surface-only) | Site arithmetic | Manufacturer span tables for board count per linear foot | Manufacturer install + fastener guidance | AWC DCA-6, IRC 2021 Ch.5 (only when guides touch structural) |
Why every output ends with four lines
Every calculator on the site outputs a Material Order Cushion: the exact math, the practical order, why the cushion exists, and when not to over-order. The math line is the geometric answer. The practical line is what I’d call the supplier with. The cushion explanation is the marginalia I wish someone had handed me on the first slab. The ceiling caveat is the part that keeps you from ordering a yard of ready-mix you can’t legally buy below the plant minimum.
Other calculators ship line one. The other three are the difference between knowing the answer and knowing the order.
What we don’t do
We don’t fabricate hobbyist anecdotes. We don’t cite publication numbers we haven’t verified — UC ANR / MSU Extension bulletins are a known LLM-confabulation hazard and every cite goes through a verify-before-write check. We don’t present AI-generated images as photographs. When a calculation has known uncertainty, we state it conservatively rather than rounding optimistically.
Questions or corrections? Contact us.