This distance should be from the top of the finished floor below and the finished floor at the top. If the floor is unfinished when you are calculating your stringers, you need to take that into account.
This measurement is sometimes called the individual rise of the stairs.
For example, if you want 7 inches (18 cm) tall stairs and your overall rise needs to be 56 inches (140 cm), then 56/7=8. You will need 8 stairs. The number of treads you have (individual runs) will automatically be one less than the number of risers.
In general, the run of each stair should be about 10 inches (25 cm) in order for people’s feet to fit comfortably as they walk up them. There are many stair calculators that you can use online to figure out stair measurements. You simply need to input your rise and the angle you want for your stairs and they will calculate the other measurements you need, including your run.
To calculate the length yourself, you will need to use the Pythagorean theorem, which is a2 + b2 = c2. So, for example, if the rise needs to be 60 inches (150 cm) and the run needs to be 84 inches (210 cm), then you would calculate 602 + 842 = c2, with “c” being the length of 99 inches (250 cm).
The short end of the square (tongue) should be on the rise measurement. The long end of the square (body) should be on the run measurement. The board should be at least 12 inches (30. 48cm) longer than the planned length of the stringer, just to give yourself some play.
Continue down the board, making sure to line up the scale’s rise and run figure at the top edge. Mark the new outline and repeat until you have marked 1 extra pair of runs and rises.
You should also clamp down your stringer board, so that it doesn’t move while you cut it.
Leave about . 5 inches (1. 3 cm) of the line uncut, which you will finish with a hand saw.
