Stair Rise and Run: Standard Riser Height, Tread Depth and How to Calculate Them

The 2015 and 2018 IRC text caps a riser at 7-3/4 in and sets a 10 in minimum tread. Divide the total rise by 7.75, round up for the number of risers, then divide again for the exact riser height.

A 108 in (9 ft) floor-to-floor rise needs 14 risers of 7.714 in, 13 treads of 10 in and a 130 in (10 ft 10 in) run. Your local code may differ, so check the edition adopted where you build.

How do you calculate stair rise and run?

risers n        = ceil( total rise ÷ max riser height )
riser height r  = total rise ÷ n
treads          = n − 1      (upper floor is the top step)
                = n          (a top tread is built)
total run       = treads × tread depth
stair angle     = atan( r ÷ tread depth )

1. Measure the total rise, finished floor to finished floor, in inches.
2. Divide it by the largest riser you want to allow (7.75 in for the limit quoted below) and round up to a whole number. That is the number of risers.
3. Divide the total rise by that number. Every riser gets this same height, which is at or under the maximum.
4. Count the treads: one fewer than the risers when the upper floor acts as the top step, or equal to the risers when you build a top tread.
5. Multiply the treads by the tread depth to get the total run. Tread depth is measured horizontally, nosing to nosing.

Rounding the number of risers up is what keeps every riser under the maximum. Rounding down would push the riser above it. The stair calculator runs these steps from your total rise and shows the run and angle. The angle is the same rise-over-run-to-degrees step explained in the roof pitch guide.

What is the standard stair rise and run?

There is no single standard, because each jurisdiction adopts its own code edition. The limits below are the ones printed in the 2015 and 2018 International Residential Code (IRC) text for new one- and two-family stairs, section R311.7, as reproduced in the American Wood Council’s DCA 6 deck guide and in county and city handouts. This guide did not open any other edition, so check the code adopted where you build, including local amendments.

The tread depth is a minimum, and you can go deeper. A 10 in tread and a 7-3/4 in riser are the extremes of the printed range, not a recommended pair. Headroom (6 ft 8 in in the 2018 text) and stair width (36 in clear in the 2015 text and DCA 6) also come from the code, but they are not part of the rise-and-run arithmetic here. The figures are quoted as printed, and this guide cannot tell you that a particular stair meets the code that applies to your project.

How do you measure the total rise (and what about a 9 ft ceiling)?

The total rise is the vertical distance from the finished surface of the lower floor to the finished surface of the upper floor. For a deck stair it runs from the deck surface to the finished grade. Measure it on site with the final flooring thickness in mind, because the code figures are measured to the finished surfaces and each riser has to stay within 3/8 in of the others.

The total rise is not the ceiling height. A 9 ft ceiling gives 108 in of clear wall below it, and the total rise to the floor above is that plus the thickness of the floor structure and finish between the two levels. That thickness varies from house to house, so this guide does not assume one. Measure it, or measure the total rise directly from floor to floor, then run the formula above. How many stairs a 9 ft ceiling needs depends on that measured figure; the table below shows how the count moves with the total rise.

How many risers, what riser height and how much run for a given total rise?

All rows use the 7.75 in maximum riser and a 10 in tread. The deck row is a 31 in rise from the deck surface to grade. The two run columns show the two ways to count treads, explained below.

The arithmetic behind the first row: 96 ÷ 7.75 = 12.39, so 13 risers; 96 ÷ 13 = 7.385 in; 12 treads × 10 = 120 in. These rows assume the total rise is measured finished floor to finished floor. A different measured rise gives a different row, so do not read a row as the answer for a given ceiling height.

How many risers do you need for a given total rise?

With a 7.75 in maximum riser, each added riser covers another 7.75 in of total rise. The count only changes when the total rise crosses one of these thresholds, which is why a small change in measured rise can add a whole step.

Each limit is the risers times 7.75: 14 × 7.75 = 108.5. A rise of exactly 108.5 in still takes 14 risers, each at the 7-3/4 in maximum. A rise of 109 in takes 15, because 109 ÷ 7.75 = 14.06.

Worked example: a 9 ft floor-to-floor rise

• Total rise: 108 in, assumed to be measured from finished floor to finished floor.
• Risers: 108 ÷ 7.75 = 13.94, rounded up to 14 risers.
• Riser height: 108 ÷ 14 = 7.714 in, under the 7.75 in maximum. On a tape that is about 7-11/16 in.
• Treads: 14 − 1 = 13 treads when the upper floor is the top step.
• Total run: 13 × 10 = 130 in, which is 10 ft 10 in. With a top tread built, 14 × 10 = 140 in.
• Stair angle: atan(7.714 ÷ 10) = 37.6°.

Rounding each riser to 7-11/16 in would give 14 × 7.6875 = 107.625 in, which is 3/8 in short of the 108 in rise. Mark with the decimal value, 7.714 in, and check the total, rather than rounding every step on the tape.

What about a deck or porch stair?

The same method applies with the total rise measured from the deck surface down to the finished grade. For a 31 in rise: 31 ÷ 7.75 = 4.0, so 4 risers of exactly 7.75 in, 3 treads and a 30 in run. A riser sitting exactly at the limit leaves no margin, so measure the real rise carefully. For decking itself, the deck calculator counts boards for the surface, and the AWC DCA 6 guide cited below covers the code limits for deck stairs, including an intermediate landing when a stairway rises more than 12 ft. Guards and handrails are not covered here.

Does the top step count as a tread?

Usually the upper floor or deck surface acts as the top step, so n risers need n − 1 treads. If you build a top tread, for example where the stringer ends on a platform that has its own tread, then n risers have n treads and the run is one tread longer. The 108 in example goes from 130 in to 140 in of run. Pick the one that matches how the stair will actually be built, because the run decides how much floor or yard the stair occupies.

Is there a comfortable rise and run?

Some design references give rules of thumb for comfort: two risers plus one tread, written 2R + T, between 24 and 25 in (Autodesk’s Revit help page, which credits Architectural Graphic Standards, and Houzz). These come from secondary sources, they are not code requirements, and they are information only. For the 108 in example, 2 × 7.714 + 10 = 25.43 in, a little over the 25 in end. A 7-3/4 in riser with a 10 in tread gives 25.5 in, so the code extremes sit slightly outside that rule of thumb. Each added riser shortens the riser and lowers the figure, and a deeper tread raises it.

Assumptions, common errors and limits

• The limits are quoted from 2015 and 2018 IRC text as reproduced in DCA 6 and in county and city handouts. Your jurisdiction may have adopted another edition or amended these values. Check with your local building department before you build.
• Using the ceiling height as the rise. The total rise is floor to floor and includes the floor structure and finish. Measure it.
• Rounding the riser count down. 13.94 risers becomes 14, never 13.
• Measuring to unfinished floors. Flooring added later changes the rise at the top or bottom step, and the 3/8 in variation limit is measured across the whole flight. Boise’s handout says the dimensions are exclusive of carpet, rugs and runners, and carpet and pad reduce the usable tread. The guide to measuring stairs for carpet covers that side.
• Confusing tread depth with tread board width. The 10 in is horizontal, between the foremost projections of adjacent treads, so it includes the nosing.
• The 2015 text does not allow one flight to rise more than 147 in between floors or landings, and this guide does not compute landings, winders, spiral stairs, headroom or width.
• This guide does not size stringers, compute spans, design handrails or guards, or check fasteners. Use the code adopted locally and a qualified professional for those.

Common questions