Valley rafter length calculator

What valley rafter length means and what the response contains

A valley rafter is the long sloping member that sits in the concave intersection of two roof planes, carrying the valley jack rafters from both sides down toward the wall plates. Unlike a common rafter, which runs straight down the slope of one plane, the valley travels on the bisector of the plan angle, so its horizontal projection is longer than the common run by the diagonal valley run factor. There is no lumber SKU catalogue, no jack layout table, and no code span table baked into the core number: you get a geometric take-off so you can add waste, seat cuts, and ridge or valley board thickness after the pure length is known. For equal pitches meeting at a right angle that factor is exactly the square root of two: valley_run equals run times root two. The vertical rise over that same common run is rise equals run times pitch over twelve, and the ridge-to-plate valley length is the hypotenuse of valley_run and rise. This calculator returns the parsed run, pitch, and overhang; a pitch_label such as six slash twelve; the valley_run_factor and valley_run; the vertical rise; the valley_pitch_factor equal to the square root of two plus unit-rise squared; the ridge_to_plate sloping length before any tail; the final valley_rafter_length; a unit tag; the precision used; a method tag; and a short formula string you can audit. Rejected cases include missing run or pitch, non-finite values, magnitudes above the documented ceiling, a zero or negative run, a negative pitch, and a negative overhang, because a non-positive run cannot define a valley line and a negative tail is not a physical eave.

How run, pitch, overhang, and precision are read and stay reproducible

Both roof planes are assumed to share that same pitch; unequal-pitch valleys need a different diagonal factor and are outside this contract. Overhang accepts overhang plus eave, tail, projection, and O; omitting it defaults to zero so a pure ridge-to-plate length is still one request. An equivalent unit method multiplies run over twelve by the square root of two hundred eighty-eight plus pitch squared, matching the classic framing table for unit valley length. Prefer run for the common horizontal distance from ridge to wall plate along one side of the valley, with aliases common_run, horizontal_run, and R so forms and query strings can reuse the same contract. Pitch accepts pitch plus aliases rise, pitch_rise, X, and roof_pitch, always as the rise component of an X-over-twelve pitch, never as degrees or as a unitless slope alone. Optional precision, with aliases decimals and dp, chooses decimal places for every numeric field in the response, defaulting to four and capped at fifteen so JSON goldens stay stable. Computation multiplies run by the square root of two for valley_run, multiplies run by pitch over twelve for rise, builds valley_pitch_factor as the square root of two plus unit-rise squared, multiplies run by that factor for ridge_to_plate, then adds overhang for valley_rafter_length. Pair the free browser run on this page with the priced API when you need the identical mathematical result inside an automated pipeline without re-implementing the valley geometry yourself.

Where valley rafter take-offs fit in DIY, trade quotes, and software

On this page the work runs entirely in your browser; through the API each successful lookup costs $0.002, failed validation is not charged, and nothing is stored after the response returns. That split — free interactive exploration and a priced, identical API — matches the rest of the KIT tier-A catalog and lets you move from a phone check on site to an automated pipeline without changing the mathematical result.