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Stair & stringer calculator

Set the finished rise, inspect the stringer cuts and carry the slope into the guard layout.

01

Enter dimensions

Top landing configuration

Planning aid only. Measure the actual site and confirm all applicable building-code requirements before ordering material or cutting a stringer.

02

Your stair layout

Layout calculated - verify all measurements on site before cutting.
Stair elevation
100%
Landing

Drag to pan · pinch or Ctrl + wheel to zoom

Horizontal run ↔
133 1/4″
Total rise ↕
108″

Run stops at the landing face. Landing depth is not included.

Calculated riser height7.7143 in≈ 7 11/16″ · 14 equal risers
Bottom stringer - first rise cut6.2143 in7 11/16″ riser minus 1 1/2″ tread thickness
Top configurationLanding is final treadUpper landing completes the flight
Number of treads13
Total horizontal run133 1/4″
Minimum tread-board depth11 1/4″Run plus nosing; add any riser-board allowance separately
Stair angle37.0°
Estimated 2×12 throat5 1/16″Actual 11 1/4-inch depth; verify required throat, species and support span
Approx. diagonal span171 1/2″
Estimated stock length16′Diagonal + 6%; verify the actual end cuts and stock
Finished rise check marks

Measure from the lower finished floor. Each mark is calculated independently; do not repeatedly add the rounded fraction.

1: 7 11/16″ · 2: 15 7/16″ · 3: 23 1/8″ · 4: 30 7/8″ · 5: 38 9/16″ · 6: 46 5/16″ · 7: 54″ · 8: 61 11/16″ · 9: 69 7/16″ · 10: 77 1/8″ · 11: 84 7/8″ · 12: 92 9/16″ · 13: 100 5/16″ · 14: 108″

These are finished tread elevations. Subtract tread thickness for stringer seat elevations.
Field referenceCut detailsBottom correction · square setup · selected top cut

Proportional details, not a full-size template. Bottom detail assumes the stringer bears on the finished lower surface. Landing support is schematic. Diagram labels are rounded; use the calculated decimal riser and cumulative elevation checks for layout.

01

Bottom correction

Bottom cut
100%
6 3/16″First tread + stringerDashed = original bottom

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Remove 1 1/2″ from the bottom. Move the level cut upward by the tread thickness, measured vertically. The red line is the new bottom cut.

6 3/16″ timber + 1 1/2″ tread = 7 11/16″ finished rise.

02

Framing-square setup

Framing square setup
100%
Run 10 1/4″Rise 7 11/16″Gauges touch the board edge

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Set the square to 7 11/16″ rise × 10 1/4″ run. The two red gauge marks sit on the same straight edge of the uncut board. Trace the outer edges, then slide the square to the next mark.

Run excludes the 1″ nosing. Board face shown cropped.

03

Standard upper cut

Top cut
100%
7 11/16″LandingBack cutFinished tops: one rise apart

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The last finished tread is 7 11/16″ below the finished landing. Its timber seat is a further 1 1/2″ below the tread top.

The red back cut runs vertically from the last seat to the lower board edge. The dashed left edge is a cropped view, not a cut. Fit the connection to the actual rim, riser boards and hanger.

StringerTreadCut

Measure twiceLay out cleanCut with confidence

Optional stair guard planner

Carry the stair geometry
into the railing.

Use the calculated stair slope to plan posts, rail stock, handrail extensions, and vertical-baluster marks. This is a material and layout aid—not a guard design or code approval.

Planning and code notice

This calculator is a layout and material-planning aid, not an engineered design or code approval. The diagrams are conceptual and do not specify hangers, fasteners, framing reinforcement, bearing, stringer quantity, material grade, headroom, guard or handrail strength, post connections, climbability, landings, or local requirements. Confirm the finished opening, connection design, materials, complete guard system, and governing code before construction.

Stair field guides

Understand the layout before you cut.

Measure the right elevations, choose the correct top configuration, and transfer the calculated geometry to a real stringer.

Measure total stair rise

Understand why finished elevations control stair comfort, how riser count affects the footprint, and when to confirm measurements before cutting.

Read guide

Choose the top mount

Choose the top-tread arrangement by the landing detail, available stair footprint and attachment, and understand what the extra tread changes.

Read guide

Correct the first stringer rise

Understand why the bottom of a cut stringer needs a tread-thickness correction, and when a change in tread or floor finish means the layout must be checked again.

Read guide

Lay out a 2×12 stringer

Learn why a test-fitted pattern, consistent reference edge and protected notch corners matter more than simply repeating rise-and-run marks.

Read guide

Avoid layout mistakes

Understand how small stair-layout errors turn into uneven steps or wasted stringers, and where a few checks can prevent repeating the mistake.

Read guide

Handrail vs. guardrail

Understand when a stair needs a graspable handrail, an edge guard or both, and how to plan them without crowding the walking route.

Read guide

Measure sloped rail

Know which stair line to measure for rails, why end returns need separate allowance, and when direct field measurements are more useful than a framing diagonal.

Read guide

Lay out stair guard posts

Balance the appearance of stair-guard bays with real anchorage, usable rail lengths and the limits of the selected railing system.

Read guide

Space stair balusters

Understand why a level-rail spacing layout cannot simply be copied onto a stair, and how plumb balusters change measurements along the slope.

Read guide