Library
All stair calculators
40 focused calculators, each with its own working tool, diagrams, worked math and answers. Every one uses the same calculation engine as the main stair calculator.
Stringers
Stair Stringer Calculator
Free stair stringer calculator: enter total rise and it gives you notch count, rise/run per step, board length and top/bottom cuts, with a diagram.
Stair Stringer Layout Calculator
Get exact stair stringer layout numbers for a framing square and stair gauges, plus a step-by-step marking procedure that avoids cumulative error.
Stair Stringer Length Calculator
Calculate stair stringer length from rise and run with the Pythagorean theorem, plus a lumber-length table so you know what to buy.
2x12 Stair Stringer Calculator
Check whether a 2x12 or 2x10 leaves enough throat depth for your stairs, plus stringer spacing guidance and closed-stringer alternatives.
Steel Stair Stringer Calculator
Calculate steel stair stringer geometry: rise/run, cut angles for channel or plate stringers, mono stringer layout, and overall fabrication length.
Deck & outdoor stairs
Deck stair calculator
Free deck stair calculator: enter deck height and get riser count, riser height, tread depth, stringer length and angle for wood or composite decks.
Deck stair stringer calculator
Calculate deck stair stringer layout: riser and tread marks, drop cut for decking thickness, and rim joist attachment for 2x12 PT stringers.
Outdoor stair calculator
Outdoor stair calculator for landscape, porch, and exterior steps: shallower risers, deeper treads, and layout tips for sloped ground.
Materials
Landings, turns & shapes
Alternating tread stair calculator
Alternating tread stair calculator for ship ladders and steep loft stairs: riser height, effective tread depth, angle, and overall run.
Stair Flight Calculator
Plan straight-flight stairs and figure out when total rise requires a landing and a second flight, with riser-split math and a rise-to-flights table.
Stair calculator with landing
Calculate a two-flight stair with an intermediate landing: risers per flight, landing depth, and each flight's own run and stringer length.
L-shaped stair calculator
Calculate an L-shaped stair with a 90-degree turn at a square landing, including per-flight risers, run, footprint, and headroom at the turn.
U-shaped stair calculator
Calculate a U-shaped (dog-leg) stair with a 180-degree turn: riser split between two parallel flights and the wider landing that reversal needs.
Winder stair calculator
Calculate winder stair treads that replace a landing: walk-line tread depth, narrow-end minimum, and a 3-winder quarter-turn layout.
Spiral stair calculator
Calculate spiral stair dimensions: risers, angle per tread, walk-line tread depth, and headroom for a given floor height, diameter, and rotation.
Rise, run & dimensions
Stair rise and run calculator
Work out riser height, tread depth and total rise and run from just the floor-to-floor height, with a table of standard residential pairs.
Stair riser calculator
Find your exact riser height and riser count from total rise, plus why every riser in a flight has to match within a tight tolerance.
Stair tread calculator
Calculate tread depth, nosing overhang, tread count and a tread board material list from your rise, run and stair width.
Stair height calculator
Measure total stair height correctly, finished floor to finished floor, and see how that single number sets your riser count.
Stair run calculator
Find the total floor space a stair needs, with and without nosing, and see your options when the available run is too short.
Stair Length Calculator
Free stair length calculator that separates total run, stringer length and overall footprint, with a riser-by-riser table and the formulas behind each number.
Stair Step Calculator
Find out exactly how many stair steps you need from a given rise, with clear riser vs. tread math, rounding logic, and a worked 66 in example.
Stair formula calculator
Every stair formula in one place: riser count, angle, stringer length, Blondel's 2R+T, headroom and notch depth, each with variables defined and worked.
Angle & slope
Stair Angle Calculator
Calculate stair angle in degrees from rise and run, see a comfortable-angle table, and get exact miter and bevel settings for stringer cuts.
Stair Slope Calculator
Convert stair rise and run into slope percentage, ratio, degrees and pitch, with formulas, a comparison table, and where slope actually matters.
Design, layout & building
Stair calculator with diagram
Free stair calculator with diagram: see the side-elevation and stringer drawing update live as you enter rise, riser and tread, then print it for the job.
Stair layout calculator
Stair layout calculator for locating the top riser, marking total run on the floor, checking headroom and laying out skirt board lines before you frame.
Stair design calculator
Stair design calculator that scores riser and tread pairs for comfort, sets stair width and nosing, and helps you choose a design before building.
Stair building calculator
Stair building calculator that turns riser and tread numbers into a materials list (stringers, treads, risers, skirt), a build sequence and common mistakes.
Stair dimensions calculator
Stair dimensions calculator covering riser, tread, nosing, width, headroom and handrail height, with a table of typical residential vs. commercial values.
Stair headroom calculator
Check stair headroom clearance and figure the floor opening length you need. Enter rise, riser, opening and floor thickness to see your clearance in inches.
Basement stair calculator
Plan basement stair dimensions, headroom, and floor opening from the slab to the floor above. Built for tight runs, existing rough stairs, and finish work.
Metric & regional
Metric stair calculator
Work stair dimensions fully in millimetres: riser, going, total run, and Blondel's 2R+G, with a quick inch-to-mm conversion table for common values.
UK stair calculator
A UK stair calculator working in millimetres, covering commonly cited Approved Document K figures for rise, going, pitch and headroom, with a worked example.
Railings, balusters & flooring
Stair railing calculator
Calculate handrail length, rail angle and post spacing for a stair railing from total rise and run, with cut angles and code-hedged height guidance.
Stair baluster spacing calculator
Calculate baluster count and even spacing for a stair rail so no gap exceeds 4 in, with a worked example and layout-stick marking method.
Stair runner calculator
Calculate how much stair runner you need from tread depth, riser height and nosing wrap, with waste allowance and Hollywood vs. waterfall install notes.
Stair carpet calculator
Calculate the carpet area for full-width stairs from tread, riser and width measurements, converted to square yards and roll cuts with waste.
Stair square footage calculator
Calculate the square footage of tread and riser surfaces on a stair for flooring, paint or refinishing estimates, with box-coverage waste guidance.
Accuracy & responsibility
Accuracy statement
StairCalculator.app is a professional stair layout tool. Every result is computed with full floating-point precision from the standard stair formulas (riser height = total rise ÷ risers; run = treads × tread depth; angle = arctan(rise ÷ run); stringer = √(rise² + run²)) and rounded only for display, to 1/16 in or 1 mm. The calculation engine is covered by automated tests and produces the same numbers a framing square, calculator or CAD package will.
Results are exactly as accurate as the measurements entered. Measure total rise finished floor to finished floor, at the point where the stair actually lands, and confirm tread thickness and stringer stock before cutting. Building codes are adopted locally and differ between jurisdictions; the IRC, IBC and UK reference limits shown are provided for checking your design, and the authority having jurisdiction has the final say.