Enter the total rise and get the number of risers and treads, exact riser height, total run, angle and stringer length, with a scaled side view and a check against US residential limits.
Divide the total rise by the riser height you want and round to a whole number: that is the number of risers, and dividing the rise by it gives the exact riser height, which must be the same for every step. A 108 in rise with a 7 3/4 in target gives 108 ÷ 7.75 = 13.9, so 14 risers of 7.714 in (7 11/16 in to the nearest 1/16 in). A flight with 14 risers has 13 treads, because the upper floor is the last tread. With a 10 in tread depth the total run is 13 × 10 = 130 in, or 10 ft 10 in. The page shows the riser as an inch fraction to 1/16 and also as a decimal and in millimetres, because the decimal is what you mark on the stringer.
The stair angle is atan(riser ÷ tread depth): 7.714 in risers on 10 in treads give 37.6 degrees. A common comfort check is 2R + T, two risers plus one tread, which should come to about 24 to 25 in (the metric form is 63 to 65 cm); it is a rule of thumb that goes back to François Blondel in the 17th century, not a code rule. Here 2 × 7.714 + 10 = 25.4 in, slightly steep. The stringer length is worked out in two parts: the length of the nosing line, from the first nosing to the last, which rises (risers − 1) × riser height over the run, √((13 × 7.714)² + 130²) = 164 in for the example, plus one step diagonal as an allowance for the plumb cut at the top and the seat cut at the bottom. That is our stated allowance, so round up to the next stock length, usually a 2 ft step: 164 + 12.6 = 176.8 in, so a 16 ft board here.
The check table uses the US International Residential Code (IRC) section R311.7 as reference values: riser at most 7 3/4 in, tread depth at least 10 in measured horizontally between nosings, headroom at least 6 ft 8 in measured up from the nosing line, clear stair width of at least 36 in above the handrails, and no more than 151 in of rise in one flight without a landing. Where the tread is under 11 in and the risers are solid, the nosing should be 3/4 to 1 1/4 in; the Open risers choice skips that check. All risers on this page are equal, so the rule that allows at most 3/8 in of variation between the tallest and shortest riser is met. The values are editable because other codes differ, for example in other countries or for stairs outside homes. The page flags numbers that fall outside them; it never says that a stair complies. Ask your building department before you cut.
It plans one straight flight. Width is only checked as clear width above the handrails; the smaller clearances at and below handrail height are not checked. It does not design winders, landings, spiral stairs, handrails, guards, headroom over the whole stair opening or the thickness of the finished floor, which changes the first and last riser. Measure the total rise after the finished floors are in, or subtract the difference when the first and last risers will change. The nosing is only used for the tread board depth and the nosing check. If the run you have is shorter than the run you need, enter it under run available and the page shows the tread depth that would fit and whether it still meets your minimum.
With a 7 3/4 in target, 14 risers of 7 11/16 in (exactly 7.714 in), which means 13 treads. With a 7 in target, 108 ÷ 7 = 15.4 rounds to 15 risers of 7.2 in.
The US IRC R311.7.5.1 sets 7 3/4 in (196 mm) as the maximum riser for homes. The page uses it as an editable reference value, and other countries and codes use different numbers, so check yours.
10 in (254 mm) in the US IRC R311.7.5.2, measured horizontally from one nosing to the next. This page calls that the tread depth or going, and the tread board is the going plus the nosing, such as 10 in plus 1 in.
The nosing line is √(((risers − 1) × riser)² + run²). For 14 risers of 7.714 in and 130 in of run that is √(100.3² + 130²) = 164.2 in. The page adds one step diagonal (12.6 in) as an allowance for the top and bottom cuts, giving 176.8 in, so buy a 16 ft board.
Two risers plus one tread should add up to about 24 to 25 in (63 to 65 cm). A 7 in riser with an 11 in tread gives 2 × 7 + 11 = 25 in. It is a comfort guide, and a stair can follow it and still break your local code.
No. The numbers are worked out in your browser, not uploaded and not stored on your device. Reloading puts the example back. The page only counts that a result was shown, without your numbers.