STAIR STRINGER DESIGN CALCULATOR - PROFESSIONAL

If you've ever cut a stair stringer you know what a pain it is.  There are multiple measurements and dimensions to consider.  It's not really all that complicated, it's just a pain.  And if you decide you want to change the number of treads in your design you have to calculate everything all over again.

There are hand-held construction calculators for this, but they cost much more, don't show you a picture, don't figure out and correct for upperdeck overhang, and you usually can't print out the final design.  For less than the price of a ruined 2x12 you can save yourself several hours of 'head scratching' and drawing on graph paper and get it right the first time with this specialty spreadsheet for stair building and basic wood stairs, such as basement stairs and deck stairs.

I've been using MS Excel every day for the last couple of decades, and so for my last set of stringers I decided it was time to get the computer to do all the work.  That way, it would be possible to try out a number of settings and see how the staircase looked before finalizing the design.  I spent several days and put it in a spreadsheet.  It made the job much easier.  I tried a few staircase designs, picked one, and cut my stringers.  It worked like a champ.

A friend wanted to use my spreadsheet, and I had to walk him through it, and explain everything.  So I spent another 100 hours getting my rough spreadsheet ready for anyone to use, with instructions, help and explanations included. 

I simplified and color-coded the main diagram of the staircase, added a scroll bar to allow super-easy changing of the number of treads, color-coded the treads and the stringer, added a diagram of the stringer all by itself with measurements, and made a nice neat list of points to mark on the stringer stock with clear step-by-step instructions.  I also cleaned up the printing so you just print out your diagrams and your cut list, and you don't have to take your laptop down to where you are working.

To design your stringers, just type in your measurements:

Upper Floor Thickness

Upper Floor Bullnose Extension (if any)

Upper Floor Bullnose Thickness

Total Rise

Total Run

Tread Thickness

Tread Depth (width)

Stringer Stock Width
 

You will see all your settings make a picture of your staircase. It calculates what the Rise/Run diagonal should be, so you can double-check your measurements, if you want.

Next, click on the number of treads (increase or decrease) and the diagram is instantly redrawn so you can see your results. There is also a list of important calculations (with suggested values) that tell you:

Angle of the Staircase (in degrees)

Rise per Step

Run per Step

Overhang of the Treads

Amount of Stringer Stock Width left uncut (to make sure you have enough strength)

How much Stringer Stock contacts the Upper Deck

How much the staircase has been adjusted out so you don't have to trim the top tread

Stringer Stock Length you need to buy
 

This spreadsheet even figures out non-90-degree cuts if your treads are smaller than the Run per Step, which eliminates the stringer stock weakening by deep square cuts.  You might use this if you want temporary stairs or lightweight stairs, say, to a boat.

You can even put in a zero for the tread thickness and make forms to pour concrete steps. 

Even if you build stairs fairly often you will still find it easier to use this spreadsheet than figuring it out manually every time, and the diagrams and graphics will impress your customers.  And if you don't want to take your computer with you to the job site, you can just call the measurements into someone with the spreadsheet at the office, and have them read the measurement back to you over your cell phone. 

Let your computer do all the figuring for you.  You won't have to buy a framing square or buttons, or dig up your trigonometry book.   Just enter your measurements, click to adjust the number of treads, print out the instructions, mark your wood, and cut. 

As situations and needs vary with every job, this spreadsheet does not give guidance on how to attach the stingers to the upper deck.  That is up to you.  Jim Self has a discussion of attachment methods at his site: http://jself.com/stair/straight/Stringer.htm as well as other tips on how to build stairs, and information on building a spiral staircase.

This spreadsheet calculates only staircases that use the upper deck as the top step, and does not handle staircases that have the top tread on the same level as the upper deck (they're not too common anyway). 

This spreadsheet does not handle or design risers but they can be easily figured in by adding them to the depth of the treads.

This spreadsheet is sold 'protected' with a password so you can't accidentally delete or overwrite anything, and to protect the formulas.  All the cells for entering your measurements are unlocked of course, and you can save your settings if you want.

Note: stair building requires a minimum level of skill, if you have never used a circular saw, and don't know what "plumb" and "level" mean, this may be a bit much for you.