StairCalc: Stair Stringer Calc

StairCalc works out a staircase from three numbers: the floor-to-floor rise, the riser height you want and the going. It gives you the step count, the exact riser height, the pitch, a cut list you can share and a live drawing you can turn in 3D. Built for carpenters, joiners and builders who want the figures before the timber is cut.

FREE AND PRO

The straight stair is free in full: every figure, the drawings, the 3D model, the cut list on screen, the regulation check with its suggested fixes, and sharing the cut list as text.
StairCalc Pro is one payment, not a subscription. It unlocks the other stair types, Timber to buy, sharing as PDF or CSV, and full-screen 3D.

STAIR TYPES

Straight flights (free). With Pro: L-shaped and U-shaped stairs with a quarter or half landing; L-winder, U-winder and C-winder stairs that turn on tapered steps instead of a landing; spiral stairs fanning from an inner pivot; and baluster spacing along a raked rail or a fixed number per tread.

WHAT YOU GET

The number of risers and the exact riser height, the total run, the stringer rake length, the pitch angle and the throat depth.
Framing-square settings: rise on the tongue, going on the body.
A cut list: stringers, treads, risers and landing boards with quantities and lengths, for cut (open) or housed (closed) stringers, with your board thicknesses.
Headroom and floor-opening length for the headroom you need.
For winders: the walkline going, the narrow width at the newel and every tapered tread's radial sides and outer edge for templating on site.
For spirals: turn per tread, inner and outer edges, and wall-stud lengths for framing the outer edge.
Timber to buy (Pro): the cut list packed into standard stock lengths with the saw cuts allowed for, so you know which boards to order.

DRAWINGS

Side-view profiles, top-down plans and a 3D model you can turn and tilt, with a choice of wood finishes and the key sizes marked on it. Full-screen 3D (Pro) turns the model with the whole screen, in landscape too. Every drawing redraws as you type.

BUILDING REGULATION CHECK

Compare your stair against Approved Document K (England: private, utility or general access stairs) or the US IRC R311.7: rise and going ranges, the 42 degree pitch limit, 2R + G, headroom, nosing, winder minimums measured where the rules say, and baluster gaps. Each check names the paragraph it comes from. When a check fails, StairCalc points at the figure to change and offers figures that pass. Spiral stairs are shown against Table 1.1 as a guide, since Part K points them to BS 5395-2. It is guidance to design by, not a substitute for Building Control or your local building department.

UNITS

Millimetres, centimetres or inches. Switching converts every figure so nothing is lost. Each stair type remembers its own figures, and Reset puts one back to its starting values. Light or dark mode, with AMOLED true black.

SHARING

Share the cut list as plain text for free, or as a PDF or a CSV that opens in a spreadsheet with Pro.

YOUR DATA STAYS ON YOUR DEVICE

No account, no sign-in, no analytics, no ads. Nothing you type is sent anywhere; the only network use is Google Play handling the optional Pro purchase.