Actual Riser Height: in
Number of Treads:
Actual Tread Depth: in
Total Run: in
Stair Angle: °
Stringer Length: in
Calculator Use
The stair calculator is an essential tool for carpenters, homeowners, and DIY enthusiasts looking to design and build safe, code-compliant staircases. By entering the total vertical rise, this tool automatically determines the number of steps required, the exact height of each riser, and the total horizontal run needed for your project.
Designing stairs requires precision; even a fraction of an inch difference between steps can create a tripping hazard. This calculator ensures all steps are identical and meet standard building regulations.
- Total Rise
- The total vertical distance from the top of the lower floor to the top of the upper floor.
- Target Riser Height
- The desired height for each individual step. Residential building codes typically suggest a maximum height of 7.75 inches.
- Tread Depth
- The horizontal distance of the part of the step you walk on. Code usually requires at least 10 inches.
How It Works
When you design a staircase, the primary goal is to divide the total height into equal increments. The stair calculator uses the following mathematical sequence:
Step 1: Total Rise / Target Riser Height = Estimated Number of Risers (Round to nearest whole number)
Step 2: Total Rise / Number of Risers = Actual Riser Height
Step 3: (Number of Risers – 1) * Tread Depth = Total Run
- Standard Layout: The top tread is one step-down from the upper floor.
- Flush Layout: The top tread is at the same level as the upper floor.
- Stringer Length: Calculated using the Pythagorean Theorem (a² + b² = c²), where 'a' is the rise and 'b' is the run.
Calculation Example
Example: Building a set of deck stairs where the ground to the deck surface is 40 inches. You want a comfortable step of about 7 inches.
Step-by-step solution:
- Total Rise = 40 inches.
- Target Riser = 7 inches.
- Calculate Risers: 40 / 7 = 5.71, round to 6 Risers.
- Calculate Actual Riser Height: 40 / 6 = 6.66 inches.
- Calculate Number of Treads: 6 – 1 = 5 Treads.
- Calculate Total Run (assuming 11″ tread): 5 * 11 = 55 inches.
- Result: You need 6 risers at 6.66″ each and 5 treads at 11″ deep.
Common Questions
What is the "7-11" Rule?
The 7-11 rule is a common building standard for stair safety. It suggests a maximum riser height of 7 inches and a minimum tread depth of 11 inches. This creates a comfortable angle for most adults and minimizes the risk of falls.
How do I measure the "Total Rise"?
To find the total rise, measure from the finished surface of the lower floor to the finished surface of the upper floor. It is critical to account for finished flooring (like hardwood or tile) on both levels, as even a 1/2 inch difference can affect the final calculation.
Why is the number of treads usually one less than risers?
In a standard staircase, the "last riser" brings you up to the floor level of the second story. Since that floor serves as the landing, you don't need a wooden tread for the very last step. This is why our stair calculator defaults to (Risers – 1) for the tread count.
What is the ideal angle for a staircase?
Standard residential stairs are usually built at an angle between 30 and 37 degrees. Anything steeper than 42 degrees is generally considered a ladder or "ship's ladder" and may not meet residential building codes for primary access.