Construction calculators

Each calculator states its formula, walks a verified worked example, and answers the questions the search result didn't. All of them run in your browser, free, in imperial or metric — and every page has a markdown mirror at the same URL with.md appended.

• Concrete Slab Calculator

  Concrete slab volume in cubic yards or cubic meters, plus 80 lb, 60 lb, or 25 kg bag counts — free, imperial + metric, with waste factor.

• Rafter Length Calculator

  Common rafter length from run and roof pitch (rise-in-12 or degrees) — line length, rise, and plumb-cut angle. Free, imperial + metric.

• Stair Layout Calculator

  Riser count, exact riser height, treads, and total run from floor-to-floor rise — with IRC and DIN 18065 comfort checks. Free, imperial + metric.