I haven’t visited the stair stringer calculator site in a while and it looks like it has been updated a bit since this original post. I can’t stress enough how much easier this will make the layout and cutting of a stair stringer. If you are building them all the time, you will learn the method, but if you build one stringer every couple of years, this calculator is invaluable. I watch people on shows like Renovation Realities and I wish that I could share this with them. The amount of material and time that is wasted without a good layout is painful to see.
If you aren’t an expert in stair building, you will probably find the math a bit of a challenge. part of the difficult part can be calculating the angle on the stair stringer where it meets the lower landing and the upper landing. There are some great tools out there to make the task of calculating a stair stringer or calculating the rise and run of stairs, but this calculator gives a great visual and even provides a cutting diagram for your stair stringer.
Take a look at this great tool.