Construction calculators
Free web calculators for the math a carpenter actually runs, each one built from the CutOnce app's tested code, with the stair calculator checked against IRC R311.7. No sign-up, works on your phone on the jobsite.
Updated
- CALC. 01
Stair stringer calculator
One total-rise measurement in, the whole stair out: riser height, tread depth, and stringer length, each checked against IRC R311.7.
Open calculator → - CALC. 02
Rafter length calculator
Span and pitch in, common rafter out: line length, ridge deduction, overhang tail, the birdsmouth seat and plumb cuts, HAP, and both saw angles.
Open calculator → - CALC. 03
Roof pitch calculator
Convert a pitch between rise per 12, degrees, percent, and ratio, in either direction, with a common-pitch conversion table.
Open calculator → - CALC. 04
Feet and inches calculator
Add, subtract, multiply, and divide feet-inch-fraction measurements the way a tape reads, rounded to the nearest sixteenth.
Open calculator → - CALC. 05
Board foot calculator
Board feet for any lumber size and quantity, figured from nominal dimensions, with a nominal-vs-actual size table.
Open calculator →
The same math the app runs
Every calculator here shares its arithmetic with the CutOnce app, and the app's numbers are checked against the app's own test suite on every build. The worked examples on each page are computed by that shared code, not typed in, so the page cannot say one thing while the calculator does another.
The whole toolbox, offline
The web pages are a taste. The app carries the full toolbox: stairs, rafters, and roof framing plus materials, concrete, drywall, decks, and unit conversions, a tape that keeps 500 calculations, and printable PDF plans, all working with no signal.
