Stair Landing Calculator
Size the landing for a straight run or a turn, and see when a flight needs one in the middle.
Code reference
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Landing width
At least the stair width
IRC R311.7.6, R311.7.7 (2024: R318.7.6)
Measured square to the direction of travel.
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Straight landing depth
36 in minimum
IRC R311.7.6, R311.7.7 (2024: R318.7.6)
Along the direction of travel on a straight run.
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Landing slope
1:48 maximum
IRC R311.7.6, R311.7.7 (2024: R318.7.6)
About 2 percent. The same limit applies to treads.
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Flight between landings
151 in maximum
IRC R311.7.3
A taller flight needs an intermediate landing.
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Deck stair height
12 ft maximum
AWC DCA 6 Figure 28
DCA 6 asks for an intermediate landing above 12 feet.
Code checks reference the 2021 International Residential Code (section numbers for the 2024 edition shown in parentheses). States and cities adopt different editions and often amend them, so limits in your area may differ.
Based on the IRC model code. Your local jurisdiction may adopt a different edition or amendments — confirm with your building department.
How to measure
Stair width
Measure the clear width of the stair above the handrail, not the rough opening. The landing has to be at least this wide, square to the direction of travel. A 36 inch stair needs a landing at least 36 inches wide. If the two ends differ, use the wider one.
Straight run or a turn
A straight landing continues in the same direction as the flight. Measure its depth along that direction. The model code asks for at least 36 inches. A turn changes direction, and each direction of travel has to be at least as wide as the stair. A 42 inch stair needs 42 inches both ways. Mark both directions before you frame the landing. This page does not lay out winders.
Which end, and how many risers
The bottom landing is the floor or pad you step onto. The top landing is the floor you leave. Count the risers. This page applies the 2024 short-stair exceptions only for Outdoor (deck). Two risers or fewer may omit the top landing. Three risers or fewer may use a bottom landing 36 inches wide even when the stair is wider. The stair has to serve a deck, porch, or yard and not be a required exit. An indoor stair does not use those exceptions.
Total rise
Total rise is finished floor to finished floor, the same measurement the stair calculator uses. Over 151 inches, the flight needs a landing in the middle. A deck stair uses the stricter 12 foot limit from AWC DCA 6, which is 144 inches. Keep the landing slope at 1:48 or less, about 2 percent.
Formula
Landing width equals the stair width. On a straight run the depth is 36 inches. On a turn the depth equals the stair width too, because each direction of travel uses the width rule. An outdoor deck stair of three risers or fewer sets the bottom width, and a turn in both directions, to 36 inches. An outdoor deck stair of two risers or fewer does not require a top landing. A flight over 151 inches needs an intermediate landing. A deck stair uses 144 inches for that split. The landing slope stays at or under 1:48.
A 36 inch straight landing is 36 inches wide and 36 inches deep. A 42 inch turn is 42 by 42. An outdoor deck stair of 2 risers does not require a top landing. A deck rise of 150 inches needs a landing in the middle.
Common mistakes
- Measuring the rough opening instead of the clear width above the handrail.
- Giving a turn only 36 inches when the stair is wider than 36 inches.
- Using the outdoor two-riser and three-riser exceptions on an indoor stair.
- Leaving a flight over 151 inches, or over 12 feet on a deck, as one run.
- Sloping the landing more than 1:48 to meet a finished floor.
FAQ
How wide and deep is a straight landing?
A straight landing is at least 36 inches in the direction of travel and at least as wide as the stair. A 36 inch stair is 36 by 36. A wider stair keeps the 36 inch depth and grows only in width. Measure the depth level, along the walking direction, from the first or last nosing to the far edge of the landing.
How big is a landing when the stair turns?
When the stair changes direction, each direction of travel has to be at least as wide as the stair. A 36 inch stair that turns needs 36 inches each way. A 42 inch stair needs 42 inches each way. Mark both directions on the floor before you frame the landing. This page does not lay out winders. A winder is a different stair, and these rules are for a flat landing.
When can an outdoor stair skip a landing?
This page applies the 2024 short-stair exceptions only when you choose Outdoor (deck). Two risers or fewer may omit the landing at the top. Three risers or fewer may use a bottom landing 36 inches wide even if the stair is wider. The stair has to serve a deck, porch, or yard, reach the ground, and not be a required exit. An indoor flight still needs a landing or a floor at both ends.
When does a flight need a landing in the middle?
The IRC keeps one flight, from floor to floor or from landing to landing, at or under 151 inches of rise. Go over that and the flight has to be split. A deck stair follows AWC DCA 6, which asks for an intermediate landing once the total rise is over 12 feet, or 144 inches. Enter the whole rise. The page says whether a middle landing is required. It does not place that landing for you.
Does a passing landing size mean the stair meets code?
No. This page sizes the landing only. It checks the stair width, the flight height, and the slope limit of 1:48. It does not check riser height, tread depth, headroom, handrails, or the stringer. Local amendments can change the landing size and the short-stair exceptions. Use the stair calculator for the risers and the opening, then confirm the landing with your building department before you frame it.
Related tools
- Plan the risers and the run for this flight Plan rise, run, and headroom before you cut.
- Lay out the stringer after the landing is sized Lay out risers, throat, and the stringer to buy.
- Count stringers for an outdoor stair Count stringers and tread boards for an outdoor stair.
- Space balusters along an open landing Space balusters on an open stair or deck edge.
- Measure the rise that decides a middle landing Measure finished floor to finished floor before you lay out a stair.
By Lumber Calc Editorial Team · Verified against 2021/2024 IRC & AWC DCA 6 · Last updated Oct 24, 2026