This stair estimator works out the rise and run of a staircase from the total height to climb, splitting it into a comfortable, code-friendly number of equal steps. It returns the riser height, tread depth (going), and the key dimensions you need to cut stringers.
Rise, run and comfortable steps
The total rise is the vertical distance from one finished floor to the next. The estimator divides it into equal risers, because steps of different heights are a serious trip hazard. It targets a riser height in the comfortable range (around 175–200 mm or 7–7¾ in) and pairs it with a tread depth that fits the well-known stair rules of thumb, such as 2 × riser + going ≈ 600–650 mm, which keeps the stair comfortable to walk.
Because the total rise rarely divides into whole steps at exactly your target height, the calculator finds the step count that gives equal risers closest to the ideal, then reports the resulting riser and going so you can check them against your local code.
From numbers to stringers
Once the riser and going are fixed, the stair's total run (horizontal length) and the stringer length follow directly. Knowing these before you cut tells you whether the stair will fit the space available and how long a board each stringer needs. Building regulations set limits on riser height, going, and pitch, so always verify the output against the rules that apply to you.
A total rise of 2600 mm with a target riser of about 180 mm.
- Steps = 2600 ÷ 180 ≈ 14.4, so use 15 risers.
- Actual riser = 2600 ÷ 15 ≈ 173 mm (equal steps).
- Pair with a ~250 mm going: 2 × 173 + 250 = 596 mm — comfortable.
Fifteen equal 173 mm risers with a 250 mm going give a comfortable, regular stair.
