Stair Calculator

The stair calculator is used for calculating stair rise and run, stair angle, stringer length, step height, tread depth, and the number of steps required for a given run of stairs.  For convenience and flexibility, this stair stringer calculator comes in two forms, the automatic  Typical Stringer and manual  Typical Stringer.  Click on the [?] icons to determine the best calculator to use for your stairs.

Automatic Stair Calculator


Input: Stair Calculator Help   
Total Rise [A] (ex: 56.75) (in)
Target Step Height [F] (in)  
Tread Thickness [C] (in)
Tread Depth [B] (in)  
Stringer Mount Type: [?] Standard Flush

Stair Results: (fraction) (decimal)
Number of Steps (risers)
Steps on Stringer [D]  
Height of First Step [E] (in)
Height of Typical Step [F] (in)
Stringer Position [H] (in)
Total Run [G] (in)
Stringer Length (in)
Stair/Rail Angle (degrees)

Typical Stringer



Manual Stair Calculator


Input: Stair Calculator Help   
Total Rise [A] (ex. 56.75) (in)  
Total Run [G] (ex. 90.5) (in)  
Number of Steps (Risers)  
Tread Thickness [C] (in)  
Stringer Mount Type: [?] Standard Flush
 

Stair Results: (fraction) (decimal)
Step Height [F] (in)
Tread Depth [B] (in)
Steps on Stringer [D]
Height of First Step [E] (in)
Stringer Position [H] (in)
Stringer Length (in)
Stair/Rail Angle (degrees)

Some results may not meet code requirements

Try adjusting the Total Rise, the Total Run, or the Number of Steps, and re-click

Calculate Stairs

Typical Stringer

Stair Calculator Results and related Building Codes**

The information below explains the stair calculator results in more detail and provides related **building code information.  If you have any questions, please don't hesitate to Contact Us.

Stringer - The stringer is the structural part of a set of stairs.  They are cut from 2x12s or larger material - the uncut portion of the stringer should not be less than 5 inches (127 mm) (see diagrams below).  In a set of stairs 36 inches wide, there are typically three stringers (one on each end and one in the middle).  The stringer length is the tip-to-tip length of the cut stringer.  It is used to determine the length of 2x12 material required to build the stair stringer.

Total Rise [A] - The total rise of a set of stairs is the vertical distance between the bottom of the first step and the top of the finished landing.  The Total Rise should be not larger than 151 inches (3835 mm) between landings or floor levels.

Total Run [G] - The Total Run is the horizontal length of a stair stringer.  It is equal to the number of treads multiplied by the typical Tread Depth [B].

Risers - the Step Height [F] is the typical height of each step.  Code states that this should not be greater than 7 3/4 inches (194 mm).  In a given run of stairs, the greatest step height and the smallest should not exceed 3/8 inch (9.5 mm).  Open risers with openings more then 30 inches (762 mm) vertical to the floor should not permit the passage of a 4-inch-diameter (102 mm) sphere.

Height of First Step [E] - The the actual finished height of the first step is the same as the Typical Step Height [F], but when you cut the stair stringer, the First Step Height [E] is always the Step Height [F] minus the Tread Thickness [C].

Treads - the Tread Depth [B] should not be less than 10 inches (254 mm).  In a given run of stairs, the greatest tread depth should not exceed the smallest by more than 3/8 inch (9.5 mm).  Typically, a single 2x12 or two 2x6s are used for stair tread material. 

Stair Stringer Diagram
Stairs with Solid Risers and 2x12 Treads

Number of Steps (Risers) - The number of risers is not necessarily the same as the number of Steps on Stringer [D].  If the Stinger Mount Type is Flush, then the number of risers is the same as the number of steps.  If the Stringer Mount Type is Standard, the number of risers will be one more than the number of Steps on Stringer [D].

Stringer Position [H] - The stringer position refers to how far below the finished height of the upper landing the stringer will be attached.

Headroom - the headroom should not be less than 6' 8" (2032 mm), measured vertically from the stair tread nosing to the nearest ceiling object.

Stair/Rail Angle - the angle is most useful for determining the bevel cut on a stair rail post.  It can also be useful for cutting the angle on the top of the stair rail pickets.

Stairs and Landings - Landings are used to break up runs of stairs.  Building code states that the minimum width of a landing should not be less than the width of the flight of stairs that is served.  **"Where the stairway has a straight run, the depth in the direction of travel shall be not less than 36 inches (914 mm)."  For additional information check out the Stairs with Landings.

** Note: Building Code information was obtained from the 2018 International Residential Code for One- and Two-Family Dwellings - Section 311 - MEANS OF EGRESS.


Click here for more information on cutting stringers and general stair building.


Mobile Stair Calculator vs. Mobile Friendly Stair Calculator

The Mobile Stair Calculator is available as always on mycarpentry.com, but I urge you to try this very webpage on your mobile or tablet device.  I hope you will find it better than my old Mobile Stair Calculator

Click here to access the old Mobile Stair Calculator.  Note, that it is designed to work only on a mobile device.  If you try to access it from laptop or notebook, it will redirect you back to this page.  Please use the contact us form for feedback.

~ Thank you!


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