How it works
Determine the riser height, number of steps, and total run for a stair stringer.
Input query strings and outputs
Use an input name in this page’s URL as ?name=value, and join additional inputs with &. Portable shared links may instead use the compact ?ac= state parameter.
Input query strings
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?totalRise=Total Rise (Floor to Floor, inches)Number · Optional · Default: 108
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?targetRise=Target Riser Height (e.g., 7 inches)Number · Optional · Default: 7
Outputs
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resultResultText · Primary output
result contains the calculator’s complete rendered result area, including its visible result cards, tables, charts, and messages.
Calculate step dimensions, riser heights, and total stair length
Description
The Stair Calculator is a specialized architectural and carpentry tool for designing safe and comfortable stairs. The most difficult part of building stairs is ensuring that every step is the exact same height—even a 1/4 inch difference can cause people to trip. This tool takes the Total Rise (the height from the bottom floor to the top floor) and your Target Riser Height to calculate the perfect layout, including the exact riser height, the number of steps, and the total horizontal “Run” required.
Inputs
- Total Rise (inches): The vertical distance between the two floor levels.
- Target Riser Height (inches): The “ideal” height you want each step to be (7 to 7.5 inches is a standard comfortable range).
Outputs
- Number of Risers: The total number of vertical lifts needed.
- Actual Riser Height: The exact height each step must be to perfectly divide the total rise.
- Number of Treads: The number of horizontal steps (usually one less than the number of risers).
- Total Run: The total horizontal space the stairs will take up (assuming a standard 10-inch tread depth).
Chart
- N/A: This tool provides precision numeric construction results.
“Good to Know”
- Building Codes: Most residential building codes require a maximum riser height of 7.75 inches and a minimum tread depth of 10 inches.
- The Ideal Step: Many builders follow the “7-11 rule” (7” riser and 11” tread) or the “Rule of 25” (Riser + Riser + Tread = 24 to 26 inches).
- Uniformity: The most important rule in stair building is that the variation between the largest and smallest riser cannot exceed 3/8 of an inch. This tool ensures they are all perfectly mathematically identical.
Examples
Example 1: Standard 9ft Ceiling
- Input: Total Rise: 108 inches, Target: 7 inches
- Output: 15 Risers, Actual: 7.200”, Total Run: 140”
Example 2: Small Porch
- Input: Total Rise: 24 inches, Target: 7.5 inches
- Output: 3 Risers, Actual: 8.000”, Total Run: 20” (Note: Risers might be too high for some codes!)
Example 3: Basement Stairs
- Input: Total Rise: 92 inches, Target: 7.25 inches
- Output: 13 Risers, Actual: 7.077”, Total Run: 120”