Stair Rise, Run and Headroom: Model-Code Dimensions
The 2021 IRC sets the riser height at no more than 7.75 in[1] and the tread depth at no less than 10 in[1], in separate sections. Every stair, handrail and guard value is quoted below with its section.
Estimates for planning, not professional advice. Read the full notice.
Work it out for your own sizes
Lay out a stairStairs
Stairway width, headroom, risers, treads, nosing and landing values from the 2021 IRC, with their section numbers
| Provision | Model-code value |
|---|---|
| Section R311.7.1: Stairway width, smallest | 36 inModel-code (2021 IRC R311.7.1) minimum clear stairway width; local adopted codes differ. |
| Section R311.7.2: Headroom, smallest | 6 ft 8 inModel-code (2021 IRC R311.7.2) minimum stairway headroom; local adopted codes differ. |
| Section R311.7.3: Vertical rise of a flight, largest | 12 ft 7 inModel-code (2021 IRC R311.7.3) maximum vertical rise of a flight of stairs; local adopted codes differ. |
| Section R311.7.5.1: Riser height, largest | 7.75 inModel-code (2021 IRC R311.7.5.1) maximum stair riser height; local adopted codes differ. |
| Section R311.7.5.1: Riser height, difference within a flight | 0.375 inModel-code (2021 IRC R311.7.5.1) maximum difference between the greatest and smallest riser in a flight; local adopted codes differ. |
| Section R311.7.5.1: Open riser opening, sphere that may not enter | 4 inModel-code (2021 IRC R311.7.5.1) open-riser opening limit above a 30 inch drop; local adopted codes differ. |
| Section R311.7.5.1: Open riser opening, drop it applies above | 30 inModel-code (2021 IRC R311.7.5.1) open-riser opening limit above a 30 inch drop; local adopted codes differ. |
| Section R311.7.5.2: Tread depth, smallest | 10 inModel-code (2021 IRC R311.7.5.2) minimum stair tread depth; local adopted codes differ. |
| Section R311.7.5.2: Tread depth, difference within a flight | 0.375 inModel-code (2021 IRC R311.7.5.2) maximum difference between the greatest and smallest tread depth in a flight; local adopted codes differ. |
| Section R311.7.5.3: Nosing projection, smallest | 0.75 inModel-code (2021 IRC R311.7.5.3) nosing projection, smallest and largest; local adopted codes differ. |
| Section R311.7.5.3: Nosing projection, largest | 1.25 inModel-code (2021 IRC R311.7.5.3) nosing projection, smallest and largest; local adopted codes differ. |
| Section R311.7.5.3: Tread depth from which the text sets no nosing projection | 11 inModel-code (2021 IRC R311.7.5.3) tread depth from which the 2021 IRC text sets no nosing projection; local adopted codes differ. |
| Section R311.7.6: Landing depth in the direction of travel, straight run | 36 inModel-code (2021 IRC R311.7.6) minimum landing depth in the direction of travel for a straight run; local adopted codes differ. |
Source: [1]
These are model-code values. The code your area has adopted may differ.
Handrails
Handrail values from the 2021 IRC, with their section numbers
| Provision | Model-code value |
|---|---|
| Section R311.7.8: Risers in a flight for which a handrail is listed | 4 risersModel-code (2021 IRC R311.7.8) number of risers in a flight for which the 2021 IRC lists a handrail on one side; local adopted codes differ. |
| Section R311.7.8.1: Handrail height, smallest | 34 inModel-code (2021 IRC R311.7.8.1) handrail height range, smallest and largest; local adopted codes differ. |
| Section R311.7.8.1: Handrail height, largest | 38 inModel-code (2021 IRC R311.7.8.1) handrail height range, smallest and largest; local adopted codes differ. |
Source: [1]
These are model-code values. The code your area has adopted may differ.
Guards
Guard height and opening values from the 2021 IRC, with their section numbers
| Provision | Model-code value |
|---|---|
| Section R312.1.1: Open side where guards are listed, drop above | 30 inModel-code (2021 IRC R312.1.1) drop and horizontal distance in the 2021 IRC text on guards at open sides; local adopted codes differ. |
| Section R312.1.1: Open side where guards are listed, distance from the edge | 36 inModel-code (2021 IRC R312.1.1) drop and horizontal distance in the 2021 IRC text on guards at open sides; local adopted codes differ. |
| Section R312.1.2: Guard height, smallest | 36 inModel-code (2021 IRC R312.1.2) minimum guard height; local adopted codes differ. |
| Section R312.1.2: Guard height on the open side of stairs, smallest | 34 inModel-code (2021 IRC R312.1.2) minimum height of guards on the open sides of stairs; local adopted codes differ. |
| Section R312.1.3: Guard opening, sphere that may not enter | 4 inModel-code (2021 IRC R312.1.3) diameter of the sphere that guard openings may not pass; local adopted codes differ. |
| Section R312.1.3: Triangle beside a stair guard, sphere that may not enter | 6 inModel-code (2021 IRC R312.1.3) diameter of the sphere the triangle at a stair guard may not pass; local adopted codes differ. |
| Section R312.1.3: Stair guard opening, sphere that may not enter | 4.375 inModel-code (2021 IRC R312.1.3) diameter of the sphere guard openings on the open side of stairs may not pass; local adopted codes differ. |
Source: [1]
These are model-code values. The code your area has adopted may differ.
What the code says
Stairs
- The 2021 IRC, section R311.7.1, says “Stairways shall be not less than 36 inches (914 mm) in clear width at all points above the permitted handrail height and below the required headroom height.”
- The 2021 IRC, section R311.7.2, says “The headroom in stairways shall be not less than 6 feet 8 inches (2032 mm) measured vertically from the sloped line adjoining the tread nosing or from the floor surface of the landing or platform”
- The 2021 IRC, section R311.7.3, says “A flight of stairs shall not have a vertical rise greater than 12 feet 7 inches (3835 mm) between floor levels or landings.”
- The 2021 IRC, section R311.7.5.1, says “The riser height shall be not more than 7 3/4 inches (196 mm).”
- The 2021 IRC, section R311.7.5.1, says “The greatest riser height within any flight of stairs shall not exceed the smallest by more than 3/8 inch (9.5 mm).”
- The 2021 IRC, section R311.7.5.1, says “At open risers, openings located more than 30 inches (762 mm), as measured vertically, to the floor or grade below shall not permit the passage of a 4-inch-diameter (102 mm) sphere.”
- The 2021 IRC, section R311.7.5.2, says “The tread depth shall be not less than 10 inches (254 mm).”
- The 2021 IRC, section R311.7.5.2, says “The greatest tread depth within any flight of stairs shall not exceed the smallest by more than 3/8 inch (9.5 mm).”
- The 2021 IRC, section R311.7.5.3, says “A nosing projection not less than 3/4 inch (19 mm) and not more than 1 1/4 inches (32 mm) shall be provided on stairways.”
- The 2021 IRC, section R311.7.5.3, says “A nosing projection is not required where the tread depth is not less than 11 inches (279 mm).”
- The 2021 IRC, section R311.7.6, says “Where the stairway has a straight run, the depth in the direction of travel shall be not less than 36 inches (914 mm).”
Handrails
- The 2021 IRC, section R311.7.8, says “Handrails shall be provided on not less than one side of each flight of stairs with four or more risers.”
- The 2021 IRC, section R311.7.8.1, says “shall be not less than 34 inches (864 mm) and not more than 38 inches (965 mm).”
Guards
- The 2021 IRC, section R312.1.1, says “located more than 30 inches (762 mm) measured vertically to the floor or grade below at any point within 36 inches (914 mm) horizontally to the edge of the open side.”
- The 2021 IRC, section R312.1.2, says “not less than 36 inches (914 mm) in height”
- The 2021 IRC, section R312.1.2, says “Guards on the open sides of stairs shall have a height of not less than 34 inches (864 mm) measured vertically from a line connecting the nosings.”
- The 2021 IRC, section R312.1.3, says “Required guards shall not have openings from the walking surface to the required guard height that allow passage of a sphere 4 inches (102 mm) in diameter.”
- The 2021 IRC, section R312.1.3, says “The triangular openings at the open side of stair, formed by the riser, tread and bottom rail of a guard, shall not allow passage of a sphere 6 inches (153 mm) in diameter.”
- The 2021 IRC, section R312.1.3, says “Guards on the open side of stairs shall not have openings that allow passage of a sphere 4 3/8 inches (111 mm) in diameter.”
In the 2024 IRC these provisions are in Sections R318.7 (stairways) and R321 (guards). The 2024 chapter.
The worked stair, row by row
The worked stair beside the quoted model-code values, one row for each comparison
| Item | This stair | Model-code value |
|---|---|---|
| Riser height: within the 2021 IRC value | 7 11/16 in | 7.75 inModel-code (2021 IRC R311.7.5.1) maximum stair riser height; local adopted codes differ. |
| Tread depth: within the 2021 IRC value | 10 in | 10 inModel-code (2021 IRC R311.7.5.2) minimum stair tread depth; local adopted codes differ. |
| Total rise of the flight: within the 2021 IRC value | 9 ft | 12 ft 7 inModel-code (2021 IRC R311.7.3) maximum vertical rise of a flight of stairs; local adopted codes differ. |
| Risers in the flight | 14 risers | 4 risersModel-code (2021 IRC R311.7.8) number of risers in a flight for which the 2021 IRC lists a handrail on one side; local adopted codes differ. |
| Tread depth, for the nosing exception | 10 in | 11 inModel-code (2021 IRC R311.7.5.3) tread depth from which the 2021 IRC text sets no nosing projection; local adopted codes differ. |
Estimate for planning, from what you entered and the product data shown. Check product labels and your supplier before you buy.
Source: 2021 International Residential Code, Chapter 3 Building Planning, International Code Council, 2021 IRC, checked Nov 12, 2026.
The stair's own sizes are this page's example, not a model-code value. A row reads within, outside or at the quoted value; where the quoted value is a threshold, a row shows the quote alone.
Questions
What is the standard rise and run for stairs?
The model code sets a largest riser height and a smallest tread depth in separate sections, and the tables above quote both with their sections. Neither section calls one riser and tread pair standard, so a layout is compared with each limit on its own.
What is the 7-11 rule for stairs?
It is a rule of thumb that pairs a riser height with a tread depth. The sections quoted above set the riser limit and the tread limit separately and do not mention the pairing, so this page compares a layout with each quoted section and leaves the pairing out.
What does the code say about landings?
One section limits the vertical rise of a flight of stairs between floor levels or landings, and another gives the depth of a landing for a straight run. Both are quoted above, and the stair calculator relates your total rise to the first one. It draws no landing layout.
What does the code say about guards on stairs?
Separate sections give the height of a guard on the open side of a stair, the size of sphere its openings may not admit, and a figure for the triangle beside the stair. All of them are quoted in the guards table above.
Calculate it for your project
Enter your own sizes to get the amount to buy or the layout figures, with the working shown and a page to print.
Work out your own stairLocal codes and amendments differ; your building department decides.
Sources (1)
-
2021 International Residential Code, Chapter 3 Building Planning (opens in new tab), International Code Council, 2021 IRC.
Code or government.
“Stairways shall be not less than 36 inches (914 mm) in clear width at all points above the permitted handrail height and below the required headroom height.”
“The headroom in stairways shall be not less than 6 feet 8 inches (2032 mm) measured vertically from the sloped line adjoining the tread nosing or from the floor surface of the landing or platform”
“A flight of stairs shall not have a vertical rise greater than 12 feet 7 inches (3835 mm) between floor levels or landings.”
“The riser height shall be not more than 7 3/4 inches (196 mm).”
“The greatest riser height within any flight of stairs shall not exceed the smallest by more than 3/8 inch (9.5 mm).”
“At open risers, openings located more than 30 inches (762 mm), as measured vertically, to the floor or grade below shall not permit the passage of a 4-inch-diameter (102 mm) sphere.”
“The tread depth shall be not less than 10 inches (254 mm).”
“The greatest tread depth within any flight of stairs shall not exceed the smallest by more than 3/8 inch (9.5 mm).”
“A nosing projection not less than 3/4 inch (19 mm) and not more than 1 1/4 inches (32 mm) shall be provided on stairways.”
“A nosing projection is not required where the tread depth is not less than 11 inches (279 mm).”
“Where the stairway has a straight run, the depth in the direction of travel shall be not less than 36 inches (914 mm).”
“Handrails shall be provided on not less than one side of each flight of stairs with four or more risers.”
“shall be not less than 34 inches (864 mm) and not more than 38 inches (965 mm).”
“located more than 30 inches (762 mm) measured vertically to the floor or grade below at any point within 36 inches (914 mm) horizontally to the edge of the open side.”
“not less than 36 inches (914 mm) in height”
“Guards on the open sides of stairs shall have a height of not less than 34 inches (864 mm) measured vertically from a line connecting the nosings.”
“Required guards shall not have openings from the walking surface to the required guard height that allow passage of a sphere 4 inches (102 mm) in diameter.”
“The triangular openings at the open side of stair, formed by the riser, tread and bottom rail of a guard, shall not allow passage of a sphere 6 inches (153 mm) in diameter.”
“Guards on the open side of stairs shall not have openings that allow passage of a sphere 4 3/8 inches (111 mm) in diameter.”
Checked November 12, 2026. Figures and codes change; verify with the source. Back to where this is used (Source 1)
These are summaries of what the sources say, not professional advice. Codes and product data change. Check with your building department and the product label about your own project.