What is the standard rise and run for stairs?
The standard rise (step height) is typically 7-7.75 inches, and the standard run (tread depth) is 10-11 inches. The sum of rise + run should equal 17-18 inches for comfortable stairs. See also our Concrete Block Calculator.
How do I calculate stringer length?
Stringer length is calculated using the Pythagorean theorem: √(total rise² + total run²). This gives you the diagonal length needed for the stair stringer board.
What angle should my stair stringers be?
Stair stringers typically have an angle between 30-40 degrees from horizontal. Angles between 32-35 degrees are most comfortable for regular use.
How many stringers do I need for my stairs?
For stairs up to 30 inches wide, use 2 stringers. For stairs 30-48 inches wide, use 3 stringers. Add one stringer for every additional 16 inches of width.
Are there building codes for stair dimensions?
Yes, most building codes require: maximum rise of 7.75 inches, minimum run of 10 inches, and consistent rise/run throughout the staircase. Check your local codes for specific requirements.
What's the difference between outside frame and flush frame attachment?
Outside frame attachment mounts stringers to the outside of the frame, while flush frame attachment sits the stringers inside or flush with the frame structure.
Can I use this calculator for deck stairs?
Yes, this calculator works for both interior and exterior stairs including deck stairs. Just ensure your measurements account for any deck height and local building codes.
What size lumber should I use for stringers?
Use 2x12 lumber for most residential stairs as it provides adequate depth for proper notching. For longer spans or heavy loads, consider engineered lumber or consult a structural engineer. You might also find our Concrete Calculator useful.