Stair Rise and Run Chart

These charts give riser counts and riser heights for common floor-to-floor heights, the tread depth that pairs with each riser height, and the US model-code limits every stair has to meet. They are for scanning and comparing. To lay out a flight from the rise you have actually measured, including total run, use the stair calculator.

Important: stairs are life-safety construction. The limits below are from the 2021 International Residential Code, and many states and cities amend them, so confirm the rules with your local building department before you cut stringers.

Maximum rise and minimum run: the IRC 2021 limits

"Rise" is the height of one riser and "run" is the depth of one tread, measured horizontally from the edge of one nosing to the edge of the next. The code puts a ceiling on the first and a floor under the second, and it limits how much either one can vary within a flight.

International Code Council, 2021 International Residential Code, Section R311.7 Stairways. Section R311.7.6 also lets you leave out the landing at the top of an interior flight when no door swings over the stairs.

Riser count and riser height by floor-to-floor height

Total rise is measured from finished floor to finished floor. For each height the chart shows the fewest risers that stay at or under 7-3/4", then the option with one more riser. The tread column uses the 2R + T = 25" rule, never going below the 10" code minimum, and the run is the number of treads times that depth. Heights are rounded to the nearest 1/16".

Two patterns stand out. At most heights the minimum riser count lands close to the 7-3/4" limit, which is legal but steep. And the extra riser costs one more tread plus a deeper comfort tread on every step, often 18" to 25" more run in total. So the choice between the two rows is usually settled by the floor space you have, not by the height.

Ceiling height is not total rise

A room with an 8 ft ceiling does not have a 96" stair. The stair climbs the ceiling height plus the floor structure above it: joists, subfloor and finish flooring. With 2x10 joists (9-1/4"), a 3/4" subfloor and 3/4" of finish flooring, an 8 ft ceiling becomes about 106-3/4" floor to floor. That is close to the 9 ft row in the chart, not the 8 ft row. Use the chart to get a feel for the numbers, then measure the real opening.

Stair tread and riser height pairs

The table applies the two carpenter's comfort rules explained in the stair calculator's FAQ at fixed targets: R + T = 17-1/2" and 2R + T = 25" (the latter usually credited to the French architect François Blondel). The angle column uses the 2R + T tread, or 10" where that tread would fall under the code minimum.

Look at where the two rules disagree. At a 7-3/4" riser, R + T gives a 9-3/4" tread and 2R + T gives 9-1/2". Both are under the 10" code minimum, so at the maximum riser the code sets the tread, not comfort. At a 6-1/2" riser the rules give 11" and 12". That spread is why neither rule is treated as exact. They point to a comfortable range, and in the 7" to 7-1/2" riser band they agree to within half an inch.

The formulas behind the charts

• Minimum risers = total rise ÷ 7.75, rounded up to a whole number
• Riser height = total rise ÷ number of risers
• Treads = risers − 1, for a flight that lands on the upper floor
• Comfort tread = 25 − 2 × riser height, but not less than 10"
• Total run = treads × tread depth
• Stair angle = arctan(riser ÷ tread)

Landings, headroom and existing stairs

Every height in the chart stays under the single-flight limit in the code table above, so none of these rows needs an intermediate landing; on the longest runs, the stairwell opening in the floor above is usually what limits the design rather than floor space. The stair calculator's FAQ covers how headroom is checked, how landings fit into the riser math, and how to compare an existing stair against the current limits.

Worked example: choosing between two rows

A new stair to a second floor has a measured rise of 114" (9 ft 6 in). The chart gives 15 risers at 7-5/8" or 16 risers at 7-1/8". For the first row, 2R + T = 25 would call for a tread of about 9-13/16", under the minimum, so the tread is 10" and 14 treads need 140" of run. The second row needs 15 treads at 10-3/4", or 161-1/4" of run, about 21" more. If the hallway allows 162", the 16-riser stair is noticeably easier to climb. If it allows only 145", the 15-riser stair is the one that fits. Enter the exact measured rise in the stair calculator to confirm the final layout before marking stringers.

FAQ

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