Guides
11 in-depth explainers on estimating materials — the formulas, the unit conversions, the waste factors, and the mistakes that leave you one bag short on a Sunday afternoon.
The calculators on this site give you a number. These guides explain where it comes from, so you can sanity-check it against your own project instead of trusting a black box. Each one shows the arithmetic in full, uses real worked examples, and cites the manufacturer data the constants come from — the same figures documented in how we calculate.
Concrete
Slabs, bags, ready-mix and thickness. Concrete is the material where getting the quantity wrong hurts most, because you cannot pause a pour halfway through to go back to the store.
Paint
Gallons, coats, coverage and what a paint job actually costs. The arithmetic is simple; the parts people get wrong are surface texture and the round-up.
Mulch, gravel & aggregate
Everything sold by the cubic yard or the ton. One identity does most of the work here — a cubic yard covers 324 square feet an inch deep — and the rest is knowing whether bags or bulk delivery wins.
Where to start
If you are new to estimating, read cubic yards to tons and bags first. Almost every material on this site is sold in a unit that isn’t the one you measured in, and that guide covers the handful of conversions the rest depend on — cubic feet to cubic yards, yards to bags, yards to tons, and the 324 identity that makes depth-based coverage easy.
If you already know what you’re building, go straight to the material: concrete, paint, mulch, or gravel.
And if the question is really about money rather than quantity, two pages answer that directly: what it costs to paint a room, DIY vs hiring a pro for a concrete slab, and concrete slab cost by size.
How these guides are written
Roughly 21,000 words across 11 guides, all of it written to be checkable. Every constant is taken from a manufacturer data sheet or an extension-service publication, independently re-derived before publication, and locked into an automated test suite so a published figure cannot quietly change. Prices are labelled as national-average estimates with the month they were set, because they are the one thing here that genuinely goes stale.
If you find an error, tell us — corrections get priority. See about for who writes this and how the site is funded.