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This is an easy stair calculator you can use to determine the rise and run of each step in your stairs and the length of boards you need to buy for your stair stringers. It also gives you the length of the opening to cut in the upper floor of your stairs so you have a minimum amount of head room when using the stairs. (This amount varies per jurisdiction.) If you want to download this stair calculator for field work, here's how.
Measure the total rise of your stairs (from the surface of the upper floor to the surface of the lower floor). You can use inches, centimeters or millimeters in the stair calculator.
Enter this amount into Stairs Total Rise and set the stair calculator for either inches or centimeters. IMPORTANT NOTE: If you are working in inches, you need to convert any feet measurements into inches. THIS CALCULATOR WILL NOT WORK IF YOU ENTER FEET AND INCHES. Examples: WRONG: 8' 2 1/2" CORRECT: 98 1/2 (just the numbers).
Optional: If you need the length of the stairs Floor Opening in the upper floor then measure the thickness of the upper floor (it might be easier to subtract the ceiling height from the total rise) and enter this into Floor Thickness of the stair calculator.
Select a common stair rise-run combination from Simple or enter your own in Custom.
Select the tread material you'll be using or enter its thickness in the space provided. (This is for the measurement of the bottom rise and how far down from the upper floor to secure the top of the stringer.
Press the Calculate button and read the results of the stair calculator in Exact Measurements
Press the Print Results button at the bottom of the stair calculator. This displays a new page with just the data results and a handy listing of measurements for the stringer markings. A little printer control panel should pop up, but if it does not, go to the File menu at the top of the stair calculator results window. Then click on Print.
Not recommended but, if you want to see what a staircase looks like that is not restricted to Building Code, then uncheck the option: Enforce Building Code Standards.
How to Use the Stair Calculator
(This includes two full-page diagrams of the stringer giving all measurements and placement.)