What is the maximum riser height allowed by code?

Under the IRC (residential), the maximum is 7¾ inches. Commercial buildings under the IBC are capped at 7 inches. Local jurisdictions can tighten these numbers but not loosen them.

Why do stairs need one fewer tread than risers?

Each riser represents a step up, but the very top step is the landing, deck, or floor itself. It doesn't need a separate tread board installed. So a 12-riser staircase has 11 physical treads.

Can my risers be different heights?

No, code allows no more than ⅜ inch of variation between the tallest and shortest riser (or tread) in a single flight. Uneven risers are a leading cause of trips and the most commonly cited code violation.

How much floor space does a staircase need?

More than most people expect. A flight covering a standard 8 ft floor-to-floor height needs about 10 ft of run with 10-inch treads, and one covering 10 ft of rise needs about 12 ft 6 in. Deeper 11-inch treads add roughly another foot. That run is needed at both the top and bottom of the flight, and a landing or a door swinging into the path adds more on top.

What is the maximum total run for a staircase?

Code sets no maximum on total run. It constrains riser height, tread depth, and the vertical rise between landings rather than horizontal distance. In practice the limit is the space available. If a straight flight will not fit, the options are a landing with a turn, winder treads, or a taller riser, in roughly that order of preference.

Do I need a permit to build stairs?

In most jurisdictions, yes, especially for exterior stairs, decks, or anything replacing a structural staircase. Check with your local building department before starting.

Stair Calculator

Enter your total rise below to calculate how many risers and treads your staircase needs, and check the result against standard U.S. residential building code before you start cutting. Getting this wrong is the single most common reason stairs fail inspection.

Total rise (in)

Target riser height (in)

Tread depth (in)

Number of risers: 12
Number of treads: 11
Actual riser height: 7.50 in
Total run: 110.0 in; 9 ft 2 in

Comfort number: 25.00; Comfortable (24-25 range)

Within IRC max riser height (7.75 in).

Meets IRC minimum tread depth (10 in).

4 or more risers: a handrail is required by code.

These flags check against IRC residential limits only. Commercial stairs fall under the stricter IBC, and some states amend these numbers locally. Always confirm with your building department.

Looking to lay out and cut the actual stringer board? Use our stair stringer calculator instead. This page is about getting the riser and tread count right first.

Why Code Compliance Comes First

Stairs are one of the most heavily regulated parts of a house for a reason: falls on stairs send well over a million people to U.S. emergency rooms every year. Under the International Residential Code (section numbers below are from the 2021 IRC, which most states adopt with only minor local amendments):

Maximum riser height: 7¾ inches (R311.7.5.1)
Minimum tread depth: 10 inches (R311.7.5.2, measured nosing to nosing)
Riser and tread uniformity: no more than ⅜ inch variation between the tallest and shortest riser, or the deepest and shallowest tread, in the same flight (R311.7.5.1 and R311.7.5.2)
Minimum stair width: 36 inches (R311.7.1)
Minimum headroom: 6 ft 8 inches (R311.7.2)
Handrail required if the stairway has 4 or more risers (R311.7.8)

Commercial buildings fall under the stricter International Building Code (IBC): 7-inch max riser, 11-inch minimum tread. If you’re building anything other than a single-family home, use those numbers instead.

The uniformity rule trips up more DIY builders than any dimension limit. A single riser that’s even a quarter-inch off from the others is the classic tripping hazard. It’s also the first thing an inspector checks with a tape measure.

Always confirm with your local building department. The IRC is a model code, and some states amend it (for example, riser and tread limits can differ slightly by jurisdiction).

How to Calculate Your Risers and Treads

Step 1: Measure Your Total Rise

Measure the vertical distance from the finished floor at the bottom to the finished floor at the top, including the thickness of any finished flooring you’ll add later, on both levels.

Step 2: Find Your Number of Risers

Divide the total rise by your target riser height (7 to 7½ inches is the comfortable range most builders aim for) and round to the nearest whole number.

Example: A deck with a total rise of 90 inches.

90 ÷ 7.5 = 12 risers

Then divide the total rise by the number of risers to get your exact riser height:

90 ÷ 12 = 7.5 inches per riser (comfortably within the 7¾-inch code maximum)

Step 3: Find Your Number of Treads

You’ll need one fewer tread than risers. The top riser lands on the deck or floor surface itself, which doesn’t need its own tread board.

12 risers − 1 = 11 treads

Step 4: Calculate Total Run

Multiply your tread count by your tread depth to find the total horizontal distance the staircase will occupy.

11 treads × 10 inches = 110 inches = 9 ft 2 in of horizontal run

How Much Floor Space a Staircase Actually Takes

Total run is the constraint that most often forces a redesign, because it is easy to underestimate. A staircase between two normal storeys eats ten to fourteen feet of floor at both the top and the bottom of the flight.

Total Rise	Risers	Riser Height	Treads	Run at 10 in	Run at 11 in
96 in (8 ft)	13	7.38 in	12	10 ft 0 in	11 ft 0 in
102 in	14	7.29 in	13	10 ft 10 in	11 ft 11 in
105 in	14	7.50 in	13	10 ft 10 in	11 ft 11 in
108 in (9 ft)	14	7.71 in	13	10 ft 10 in	11 ft 11 in
112 in	15	7.47 in	14	11 ft 8 in	12 ft 10 in
120 in (10 ft)	16	7.50 in	15	12 ft 6 in	13 ft 9 in

The 108-inch row is worth looking at closely. Fourteen risers at that height works out to 7.71 inches. That is legal, but it leaves four hundredths of an inch to spare against the 7¾ maximum. Any error in measuring the total rise, or a finished floor thickness that was not accounted for, pushes that flight out of compliance. When the arithmetic lands that close to the limit, add a riser rather than hoping the measurement was perfect.

Two things this table does not include, both of which add to the space required:

Landing at the bottom or top. A door that swings into the stair path, or a flight that ends facing a wall, needs a landing at least as deep as the stair is wide.
Headroom clearance. The 6 ft 8 in minimum is measured from the nosing line, and it constrains the opening in the floor above rather than the stair itself. A stairwell opening that is too short puts the lowest headroom at the top of the flight, where a descending person meets the header.

When a Straight Flight Doesn’t Fit

If the run does not fit the space, the options are limited and each has a cost.

Add a landing and turn. An L-shaped or U-shaped flight fits the same rise into a shorter footprint by folding it. The landing itself consumes space equal to the stair width, and it counts as neither riser nor tread, so the total rise is unchanged but the flight becomes two.

Use winders. Wedge-shaped treads turn the flight without a full landing, saving the most space. They come with restrictions: the tread must give at least 10 inches of depth measured 12 inches in from the narrow end, and at least 6 inches at any point, which rules out a true pie slice. Winders are also the least comfortable option underfoot and the most awkward to carry furniture on.

Increase the riser height. Going from 7 to 7½ inches reduces the riser count and shortens the run. This is the tempting option and usually the wrong one. It trades a permanent daily inconvenience for a one-time space saving, and it pushes you closer to the code limit with no margin for error.

What is not an option is reducing tread depth below the 10-inch minimum. That is where inspectors look first, and it is the dimension most directly connected to falls.

For the full set of code figures (headroom, handrail and guard heights, winder and landing requirements, and where the IBC differs), see our stair code requirements guide.

Does It Pass, and Does It Feel Right?

Code sets the outer boundary. Within it there is a long-standing ergonomic check: 2 × riser height + tread depth should land between 24 and 25 inches.

For the example above, (2 × 7.5) + 10 = 25, right at the top of that range. A flight can pass inspection and still feel wrong underfoot, which matters on a staircase people use every day rather than once a year. The reasoning behind the formula, and where it sits against the code limits, is covered in the stair code requirements guide.

Frequently Asked Questions

What is the maximum riser height allowed by code?: Under the IRC (residential), the maximum is 7¾ inches. Commercial buildings under the IBC are capped at 7 inches. Local jurisdictions can tighten these numbers but not loosen them.
Why do stairs need one fewer tread than risers?: Each riser represents a step up, but the very top step is the landing, deck, or floor itself. It doesn't need a separate tread board installed. So a 12-riser staircase has 11 physical treads.
Can my risers be different heights?: No, code allows no more than ⅜ inch of variation between the tallest and shortest riser (or tread) in a single flight. Uneven risers are a leading cause of trips and the most commonly cited code violation.
How much floor space does a staircase need?: More than most people expect. A flight covering a standard 8 ft floor-to-floor height needs about 10 ft of run with 10-inch treads, and one covering 10 ft of rise needs about 12 ft 6 in. Deeper 11-inch treads add roughly another foot. That run is needed at both the top and bottom of the flight, and a landing or a door swinging into the path adds more on top.
What is the maximum total run for a staircase?: Code sets no maximum on total run. It constrains riser height, tread depth, and the vertical rise between landings rather than horizontal distance. In practice the limit is the space available. If a straight flight will not fit, the options are a landing with a turn, winder treads, or a taller riser, in roughly that order of preference.
Do I need a permit to build stairs?: In most jurisdictions, yes, especially for exterior stairs, decks, or anything replacing a structural staircase. Check with your local building department before starting.

This calculator provides planning estimates based on the International Residential Code. Building codes vary by state and municipality. Always verify final dimensions with your local building department before construction, and consult a licensed contractor for structural stairways.

Written by: The CubedCalc Team. We research and fact-check every calculator using manufacturer specs, building codes, and industry references. We are not licensed contractors or engineers; always verify code-critical dimensions with your local building department or a licensed professional before construction.