SiteCalc
Ten offline construction calculators that draw a to-scale diagram as you type. On Google Play as Stair & Rafter Calculator.
The product
Carpenters work in feet, inches and sixteenths — on job sites with no signal. SiteCalc gives them ten fully-offline calculators (stairs, rafters, concrete, decks, fencing, drywall, framing and more) where every answer is drawn as a to-scale diagram next to the numbers: draw your stringer before you cut it.
The engineering is deliberate: a custom feet-inches-fraction engine and keypad with its own input grammar, a canonical-inches architecture that re-renders saved projects in metric for free, and a declarative calculator framework where each new calculator is just inputs + results + a painter.
Under the hood
THE ENGINEERING
- 01
Custom fraction keypad and 528-line measurement engine — accepts 9' 1", 109, or 9 1/2 and always rounds to buildable fractions
- 02
Every calculator renders a live CustomPainter diagram — stringers, rafter triangles, slab layouts — tested across 2 themes × 7 canvas sizes
- 03
Built to a numbered 598-line spec whose acceptance table is asserted on displayed strings, not floats — formula drift fails a test first
- 04
IRC residential code checks built into the stairs calculator
- 05
Share-cards rasterised to PNG with watermark; rewarded-ad export that still succeeds free if the ad fails (and that fallback is tested)
- 06
A release-only launch crash caught before upload: R8 stripped a class that Room loads by name, and keep rules fixed it
- 07
TalkBack labels on inputs and results, 48 dp touch targets and high-contrast text for reading in direct sunlight
In the product
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