How to plan a straight staircase.
A straight (single-flight) staircase climbs from one floor to the next in one continuous run, with no turn. It's the simplest stair geometry, the cheapest to build, and — when there's enough length to fit it — the most comfortable to walk.
When is a straight stair the right choice?
A straight flight needs roughly 2.5–3 m of clear horizontal length for a typical floor-to-floor height of 2.8 m. If your room offers that much uninterrupted floor depth, a straight stair is hard to beat: no winder treads to compromise the walking surface, no landing to add length, and a structurally simple two-stringer carcass any joiner can build. If you're tight on length, switch to the L-shaped, U-shaped, or ladder calculator linked on the right.
Four rules to get right before you cut wood
- Rise per step ≈ 170–185 mm. Comfortable for daily use. Anything above 200 mm becomes tiring; below 140 mm wastes vertical space.
- Tread depth ≥ 230 mm. Your foot needs landing space. With a 30 mm front overhang you can cheat the going down to 250 mm, but never less.
- 2 × rise + tread = 580–650 mm. The classic stride formula (Schrittmaß). Stay inside this band and the stair will feel right under any leg length.
- Headroom ≥ 2.0 m. Measured perpendicular from any tread nosing up to the ceiling or upper-floor opening edge. On a straight stair the headroom is tightest near the top — keep enough opening in the upper floor.
Closed vs. open stringers
Closed stringers are solid side boards with the treads and risers let into dadoed pockets. This is the classic interior-residential look: clean side faces, hidden joinery, full sound insulation. Mortise-and-tenon connections into the newel posts are generated only with closed stringers.
Open (saw-tooth) stringers have the tread profile cut directly into the top edge, so the treads sit on top of the saw-tooth and the side of each step is visible. This is the lighter, more modern look — popular for open-plan rooms — but it skips the tenon joinery between stringer and post; the carpenter details those connections on site.
How to read the live preview
The 3D view is purely illustrative — useful for sharing with a client or spouse. The 2D Top view is what your carpenter needs to verify the stair fits the room. The X-Ray view shows the stringer / dado joinery without removing surrounding parts. All three update from the same geometry model the moment you change a slider on the left.
What you'll get when you export
Every export speaks back to the live geometry above — the moment you tweak a parameter, the next download reflects the change. Five formats are available:
- PDF · multi-sheet A3 construction drawing. A3 landscape, ready to print. Sheets cover the project summary, plan view, side elevation, scaled workshop drawings for stringers / treads / risers / newels / handrail / balusters with dado and mortise pockets, and a bill of materials. Drawings are scaled to fit A3 (typically 1:10 or 1:20 depending on the part) — use this PDF as the on-site reference and quote document, not as a cutting template.
- DXF · 1:1 CAD/CNC zip. One file per category (plan, elevation, each part family) at true 1:1 scale in the chosen unit — every contour is the actual cut path. Named layers separate stringers, treads, risers, newels, handrail, balusters, dado and mortise cutouts. Loads straight into AutoCAD, BricsCAD, LibreCAD, and any CNC post-processor as workshop-ready templates.
- SVG · 1:1 vector zip. Same drawings as the DXF, also at true 1:1 scale, but as plain SVG — open in any browser, Illustrator, Inkscape, or Affinity Designer. Useful for clients who don't have CAD installed, or for laser cutters that prefer SVG input.
- STL · 3D printable mesh. A single solid model for slicing and 3D printing the design as a tabletop reference, or for importing into visualization tools (Blender, Twinmotion, Lumion).
- STEP · parametric CAD exchange. Each part — every stringer, tread, riser, newel, handrail piece, baluster — as a separate body with its mortise and dado pockets baked in as proper B-Rep solids. Opens natively in SolidWorks, Inventor, Fusion 360, FreeCAD, and SolidEdge for further design work or assembly checks.
What the files do not include
The downloads are a construction foundation, not a turnkey product. Depending on your specific configuration, joinery details (tenon shoulders, post mortises, baluster sockets) and stringer-to-newel connections may need minor on-site adjustments by your carpenter. The geometry pipeline is conservative — when in doubt it errs on the side of clear space — so the parts will fit, but the final aesthetic millwork (chamfers, fillets, plug covers, sanding profiles) is up to whoever builds it. Always verify all dimensions on site before cutting wood.
Two scope notes specific to this calculator:
- Mortise-and-tenon joinery is only generated with closed stringers. Open (saw-tooth) and no-stringer configurations rely on surface-mounted treads and skip the tenon / dado pockets — the part outlines stay correct, but post-to-stringer connections must be detailed by your carpenter.
- Handrail and balusters are orientation-only. They define positions, lengths, angles, and cross-section sizes so the parts list and plan reflect reality — but the drawings do not include the joinery itself (newel-post mortises for the handrail, baluster drill sockets, dowel pins, anchor screws). Use them as a layout reference and detail the connections during install.