SettingsSettings for this calculationUS
Finished floor below to finished floor above.
Measured on site once the floors are framed, with the finishes each floor will carry; the risers share it equally.
Tools needed: Tape measure, Spirit level
The rise per step you want; the page rounds the count up so no riser is taller.
The count of risers is the total rise over this, rounded up, and every riser is then the total rise shared equally, so each comes out at or under the figure entered. Your code sets the most a riser may be.
The horizontal step from one nosing to the next, the same on every flight.
The going sets each flight's run and so each stringer's length. Your code sets the least it may be.
The flight's width, which is also each tread's length and a quarter landing's side.
The IRC asks for a landing no narrower and no shorter than the stair it serves, so a quarter landing is this width square and a half landing twice it by once.
Where the stair turns, and on what.
A quarter landing turns the stair through a right angle; a half landing turns it right round between two flights side by side; two quarter landings turn it right round with a short flight between them.
A flat landing at each turn, or winders that keep climbing round it.
Winders take the same square as a quarter landing (a half turn, two of them) and climb a riser each, so the stair needs less run; each is a tread. Your code sets how deep they must be at the walk line and at the narrow end.
How many risers climb to the first landing (or first winder), counting the one up onto it.
The landing's height is these risers times the rise. The rest of the risers go in the later flights; a figure past the stair's own count is held to it.
How many stringers your plan puts under each flight.
Two at the sides and one in the middle is common on a house stair; the number that carries your treads is the plan's, read from the tread's span.
The centres of the joists across each landing.
The landing is framed as a rim round its edge with joists across between; the deck over it is cut from the landing area row.
One rim member's thickness; the joists are cut between the rims.
A 2x member is 1 1/2 in (38 mm).
Treads
13 treads
15 risers of 182.9 mm in flights of 8, 7; each flight's top step is a landing or the floor, so the treads are the risers less one per flight. Check the riser, going and landings against your code on the stair rise and run page.
- Risers
- 15 risers
- Each riser
- 7.2 in
- Two risers and a going
- 24.65 in
- Flights
- 2 flights
- Landings
- 1 landing
- Height of the first landing
- 4.8 ft
- Stringers
- 6 stringers
- Longest stringer line
- 7.67 ft
- Stringers, lineal
- 42.88 ft
- Tread boards, lineal
- 39 ft
- Winders
- 0 treads
- Area of the winder turns
- 0 sq ft
- Landing area
- 9 sq ft
- Landing rims, lineal
- 12 ft
- Landing joists
- 2 joists
- Landing joists, lineal
- 5.5 ft
They open the calculator with your figures already in it
L-Shaped and U-Shaped Stair Calculator (Landings, Winders, Stringers, Treads and Risers): 13 treads — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
Show calculation logicHide calculation logic
How this was calculated
Formula source(s)
- Permit Sonoma, Technical Bulletin B-09, Code Requirements for Residential Stairs (2020 to current, California Residential Code): R311.7.1 stairways at least 36 inches wide; R311.7.3 no more than 151 inches vertically between landings; R311.7.5 risers no more than 7.75 inches and treads no less than 10 inches; R311.7.6 a floor or landing at the top and bottom of each stairway, its width and length no less than the stairway's width; winders a tread depth of 10 inches at the walk line and at least 6 inches
- Stringer line length = sqrt(rise² + run²) over the flight it carries, the right-triangle geometry of this site's stringer length page; the risers shared equally over the total rise, as this site's stair rise and run page divides them
Inputs used
- Total Rise (floor to floor)
- 9 ft
- Riser You Are Aiming For
- 7.25 in
- Going (tread depth, nosing to nosing)
- 10.25 in
- Stair Width
- 3 ft
- Stair Shape
- L-shaped: one quarter landing
- The Turn Is Made On
- A flat landing
- Winders in Each Quarter Turn
- 3
- Risers in the First Flight
- 8
- Risers in the Middle Flight
- 3
- Stringers Under Each Flight
- 3
- Landing Joist Spacing
- 16 in
- Landing Rim Thickness
- 1.5 in
Intermediate steps
- Risers
- 15 risers
- Each riser
- 7.2 in
- Two risers and a going
- 24.65 in
- Flights
- 2 flights
- Landings
- 1 landing
- Height of the first landing
- 4.8 ft
- Stringers
- 6 stringers
- Longest stringer line
- 7.67 ft
- Stringers, lineal
- 42.88 ft
- Tread boards, lineal
- 39 ft
- Winders
- 0 treads
- Area of the winder turns
- 0 sq ft
- Landing area
- 9 sq ft
- Landing rims, lineal
- 12 ft
- Landing joists
- 2 joists
- Landing joists, lineal
- 5.5 ft
Confidence note: 15 risers of 182.9 mm in flights of 8, 7; each flight's top step is a landing or the floor, so the treads are the risers less one per flight. Check the riser, going and landings against your code on the stair rise and run page.
What this calculation does not cover
- This counts a stair; it does not approve one. The riser, the going, the width, the headroom and the landings are your code's, checked on the stair rise and run page or by your building official, and nothing here says a stair complies.
- Each stringer is the line from the flight's foot to its landing or floor. The board it is cut from must be longer by the cuts at both ends and deep enough to keep the throat your plan requires, which this does not add.
- Landings are flat and square-cornered: a quarter landing the stair's width square, a half landing twice the width by one. A gap between the flights of a U and a landing longer than the stair is wide are not drawn; enter such a landing's framing by its own measure.
- Winders are counted, not set out: how deep each is at the walk line and at its narrow end is your code's (10 in at the walk line and 6 in at least in the IRC's terms, as Permit Sonoma's bulletin puts them), and a turn of three winders set out from the corner post is often too narrow there. The carriages or blocking that carry them, and the boards each is cut from, are not counted; the area of the turns is given for the boards.
- Landing framing is a rim round the edge and joists across at the spacing entered. The posts, hangers or ledgers that carry the landing depend on whether it stands free or hangs from walls, and are not counted.
- Risers are counted as boards; an open-riser stair has none. Nosings, balusters, handrails, the newels at each turn, the skirting and the finishes are separate items.
Estimated cost — your price
This site holds no price list for this material — local prices vary too much to publish honestly. Enter your supplier's price and the result is costed with it.
Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.
Sources checked 2026-10-11 · v1.0.0
Regulatory standards & verification citations2
- Permit Sonoma, Technical Bulletin B-09, Code Requirements for Residential Stairs (2020 to current, California Residential Code): R311.7.1 stairways at least 36 inches wide; R311.7.3 no more than 151 inches vertically between landings; R311.7.5 risers no more than 7.75 inches and treads no less than 10 inches; R311.7.6 a floor or landing at the top and bottom of each stairway, its width and length no less than the stairway's width; winders a tread depth of 10 inches at the walk line and at least 6 inches
- Stringer line length = sqrt(rise² + run²) over the flight it carries, the right-triangle geometry of this site's stringer length page; the risers shared equally over the total rise, as this site's stair rise and run page divides them
Cite this page
Your workspace
Most jobs need more than one number. Add the calculators you need next and they open right here, underneath this one — your figures stay on screen and nothing is lost to a page change.