By Avery Schwartz — builder of HouseMath, AxleMath, and ToolboxMath.
HouseMath exists because of the second trip to the store. Everybody who's ever mulched a yard knows it: you eyeball the beds, guess "ten bags," and at 4 p.m. you're back in the garden aisle buying the eleventh and twelfth. I build calculator sites for a living now — I started with AxleMath, the trucker math site, after three years of driving — and this one is aimed at exactly that problem: turning a home project into a shopping list before the first trip.
I'm not a landscaper or a flooring installer, so HouseMath doesn't run on my opinions. Every coverage number traces to the figures the industry itself publishes: a 2-cubic-foot bag of mulch covers 12 square feet at 2 inches deep because that's the arithmetic of volume, a gallon of paint covers about 350 square feet because that's the number on the back of virtually every can, sod comes in rolls and pallets the way farms actually cut it, and waste factors follow the standard installer conventions — 10% for straight-lay flooring, more for diagonal and tile. Where products genuinely vary, the tools say so, and the rule printed on every page is the honest one: if your product's label disagrees with this site, the label wins.
Every calculator here ends the same way: a shopping list in the units the store sells — bags, gallons, boxes, rolls, sticks, pallets — with the waste allowance shown, the formula printed, and the assumptions in plain sight. Nothing to install, no account, and nothing you type ever leaves your browser.
Corrections
If a coverage rate or formula here doesn't match what the job actually took, that's a bug and I want it. Send the calculator name and your inputs through the contact page — error reports get fixed first.