FAQ

Every calculator implements a formula traced to an authoritative source and tested against a documented worked example, and unit conversions use exact NIST SP 811 factors. Every formula and every constant it relies on — a material density, an industry pack size, a code value — is cited on the calculator's page, so nothing is shipped on guessed math.

The exact result is the pure math of your inputs. The recommended result adds a visible, editable waste allowance so you order enough. They are always shown separately with the percentage between them.

Yes, for calculators you have already opened. The engine and calculator definitions are cached, so calculations, unit conversion, favorites, recently used and saved calculations all work with no signal. Source links refresh when you reconnect.

No. Favorites, recently used and saved calculations are stored on your device. Cloud sync is a future feature and the data is already structured for it.

Both, on every calculator. The global toggle converts every value on screen in place and never clears your inputs.

97 live calculators across 19 categories — concrete, roofing, framing, masonry, tile and flooring, landscaping, drainage, stairs, walls, siding, fencing, painting, materials (including aggregate and soil testing) and more. Each one carries its formula, a worked example that runs as a test, its assumptions and its sources. The library is built to grow, and any calculator added later ships the same way: sourced and tested first, live second. The five structural calculators (snow load, wood beam span, floor joist, door header, roof truss) additionally carry an estimate-only notice — they are not an engineering sign-off.