Stair stringer notch layout

Choose unit rise and unit run, then mark the notch

Send rise as a strictly positive finite number; aliases unit_rise, riser, riser_height, unit_riser, and riser_notch map to the same field for shorter form labels. Send run the same way with aliases unit_run, tread, tread_depth, going, unit_going, and tread_notch. Zero or negative dimensions raise invalid_input and are not charged, because a non-positive leg cannot define a real notch triangle for layout. Extremely small or huge values outside the published stability range also fail so floating-point results stay meaningful on a Worker isolate.

How riser notch, tread notch, diagonal, throat and layout length are computed

The engine treats each step as a right triangle whose vertical leg is unit rise and whose horizontal leg is unit run. Together those two legs are what a framing square is set to when you walk notches along the board. Pitch_angle_deg is the arctangent of rise over run converted to degrees from the horizontal via a two-argument arctangent so the angle stays sensible for positive legs. The riser_notch field equals rise: that is the vertical distance you mark on the stringer for the riser face of the notch. The tread_notch field equals run: that is the horizontal distance you mark for the tread face. The step_diagonal is the hypotenuse, the square root of rise squared plus run squared, and it is the centre-line spacing along the stringer from one full step mark to the next. When you also send stringer_width—the stock width of the board measured across its face—the calculator reports notch_depth as the altitude from the right-angle corner of the rise-run triangle to the hypotenuse, equal to rise times run divided by step_diagonal, and throat as stringer_width minus that notch depth. Throat is the remaining solid wood after the notch is cut, measured in the same unit; if the board is too narrow and throat would not be positive, the request fails with invalid_input so you do not mark an impossible cut. When step_count is provided as a positive integer (aliases riser_count, number_of_risers, steps, num_steps), layout_length equals step_count times step_diagonal for a quick cumulative mark length along the stringer. The payload always echoes cleaned rise and run, sets formula to the notch and diagonal identities, and labels method as stringer_notch_layout for stable client branching. Identical inputs always produce identical JSON because the path is pure arithmetic with no network, random seed, or wall clock.

API usage, pricing, site workflows and practical limits

Call the free in-browser stair stringer notch layout calculator for quick home layout, contractor whiteboards, and classroom framing demos without opening a spreadsheet. Remember that nosing projection, finished floor thickness, and how you seat the bottom and top of the stringer against landings can change effective geometry even when unit rise and run look settled—adjust inputs to match the geometry you will actually mark. Send a JSON body with required rise and run as finite positive numbers or numeric strings, and optionally stringer_width and step_count. Use the prepaid API when a renovation app, takeoff tool, configurator, or property pipeline needs a stable contract under KIT balance at $0.002 per successful item; validation failures never consume balance after the engine rejects the request. Pair this endpoint with a staircase step calculator when you still need riser count and exact riser height from storey height, or with a stair stringer length calculator when you need the overall diagonal of the full flight from total rise and total run. Authors shipping SDKs can map riser_notch and tread_notch into cut lists while showing step_diagonal, pitch_angle_deg, throat, and formula as explanatory detail for the homeowner or site supervisor reviewing the layout before timber is ordered.