Stair stringer length calculator

Measure total rise and total run in one unit system

Total rise is the finished floor-to-floor or landing-to-landing vertical distance the flight must climb. Measure from the top of the lower finished surface to the top of the upper finished surface after you know floor finishes, or adjust the design rise if finishes will change later. Total run is the overall horizontal going of the flight—the sum of the tread goings from the face of the first riser line to the face of the last, or the plan distance your layout already fixed. Express both values in the same linear unit because the calculator never converts systems: if total_rise is two thousand eight hundred millimetres, total_run must also be millimetres. Send total_rise as a strictly positive finite number; aliases rise, height, total_height, and vertical_rise map to the same field for shorter form labels. Send total_run the same way with aliases run, horizontal_run, going_total, and total_going. Zero or negative dimensions raise invalid_input and are not charged, because a non-positive side cannot define a real right triangle for the stringer hypotenuse. Extremely small or huge values outside the published stability range also fail so floating-point results stay meaningful on a Worker isolate. If plans list only storey height and individual tread goings, multiply tread depth by tread count (or step count minus one, depending on your convention) to obtain total run before calling this endpoint.

How stringer length and pitch angle are computed

The engine treats the flight as a right triangle whose vertical leg is total rise and whose horizontal leg is total run. Treat the result as the theoretical centre-line or layout length of the sloping member, then apply your local framing practice when marking the board. The stringer cut length is the hypotenuse: the square root of the sum of the squares of those two legs, written stringer_length equals the square root of total_rise squared plus total_run squared. That is the classical Pythagorean theorem applied to stair geometry, and it is unit-agnostic: the output length uses the same unit you used for both inputs. Alongside the length, the response reports angle_deg, the pitch angle from the horizontal in degrees, computed as the arctangent of rise over run via a two-argument arctangent so the angle stays in a sensible open interval for positive legs. The payload echoes cleaned total_rise and total_run, sets formula to the square-root identity, and labels method as pythagorean_stringer for stable client branching. Identical inputs always produce identical JSON because the path is pure arithmetic with no network, random seed, or wall clock. This product does not enforce code maxima for riser height, going depth, or headroom, and it does not subtract stock thickness, birdsmouth notches, or landing overlaps—those are site layout decisions after you know the geometric diagonal.

API usage, pricing, takeoff workflows and practical limits

Call the free in-browser stair stringer length calculator for quick home estimates, contractor whiteboards, and classroom statics demos without opening a spreadsheet. Remember that finished floor thickness, nosing projection, and how you measure run to the face of the last riser can change effective geometry even when structural numbers look settled—adjust inputs to match the geometry you will actually cut. Send a JSON body with required total_rise and total_run as finite positive numbers or numeric strings. 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 unit converters when drawings mix millimetres with inches. Authors shipping SDKs can map stringer_length into cut lists while showing angle_deg and formula as explanatory detail for the homeowner or site supervisor reviewing the layout before timber is ordered.