📐 Stair Calculator
Calculate stair dimensions and stringer length
Vertical distance from bottom to top of stairs
How to Use This Calculator
Enter Total Rise
Input the total vertical distance from the bottom of the stairs to the top landing in inches. Measure from the finished floor below to the finished floor above.
Select Desired Riser Height
Choose your desired riser height in inches. Standard is 7.5 inches (comfortable). Maximum is 8 inches (building code). The calculator will adjust to fit your total rise.
Specify Tread Depth and Width
Select tread depth (standard 10 inches) and stair width (standard 36 inches). Tread depth minimum is 9 inches (building code). Wider stairs are more comfortable.
Calculate and Build
Click "Calculate Stairs" to see number of steps, actual riser height, total run, and stringer length. Use these dimensions to cut stringers and build stairs.
Formula
Number of Risers = Total Rise ÷ Desired Riser Height (rounded up)
Actual Riser Height = Total Rise ÷ Number of Risers
Number of Treads = Number of Risers - 1
Total Run = Number of Treads × Tread Depth
Stringer Length = √(Total Run² + Total Rise²)
Example 1: Standard Stair (96 inches total rise, 7.5 inch riser, 10 inch tread)
Step 1: Calculate risers: 96 ÷ 7.5 = 12.8 → 13 risers
Step 2: Actual riser height: 96 ÷ 13 = 7.38 inches
Step 3: Calculate treads: 13 - 1 = 12 treads
Step 4: Total run: 12 × 10 = 120 inches (10 feet)
Step 5: Stringer length: √(120² + 96²) = √(14,400 + 9,216) = √23,616 = 153.7 inches
Step 6: Rise + Run: 7.38 + 10 = 17.38 inches ✓ (within 17-18" code requirement)
Example 2: Taller Stair (108 inches total rise, 8 inch riser, 11 inch tread)
Step 1: Calculate risers: 108 ÷ 8 = 13.5 → 14 risers
Step 2: Actual riser height: 108 ÷ 14 = 7.71 inches
Step 3: Calculate treads: 14 - 1 = 13 treads
Step 4: Total run: 13 × 11 = 143 inches (11.9 feet)
Step 5: Stringer length: √(143² + 108²) = √(20,449 + 11,664) = √32,113 = 179.2 inches
About Stair Calculator
The Stair Calculator is an essential tool for contractors, builders, carpenters, and DIY enthusiasts who need to accurately calculate stair dimensions for their construction projects. This calculator eliminates guesswork by providing precise riser heights, tread depths, total run, and stringer length calculations, ensuring your stairs meet building codes and are safe and comfortable to use.
When to Use This Calculator
- New Stair Construction: Calculate stair dimensions for new stairs in homes, decks, or buildings
- Stair Replacement: Determine dimensions for replacing existing stairs or staircases
- Deck Stairs: Calculate dimensions for deck stairs or exterior stairs
- Basement Stairs: Estimate dimensions for basement stairs or cellar stairs
- Building Code Compliance: Ensure stairs meet building code requirements for risers, treads, and dimensions
Why Use Our Calculator?
- ✅ Building Code Compliance: Ensures stairs meet code requirements (riser 6-8", tread 9+", rise+run 17-18")
- ✅ Accurate Calculations: Precise riser and tread dimensions prevent unsafe or uncomfortable stairs
- ✅ Stringer Length: Calculates exact stringer board length needed for cutting
- ✅ Total Run: Determines horizontal space needed for stairs
- ✅ Customizable: Adjust riser height and tread depth to meet your needs and space constraints
- ✅ Time Savings: Instant calculations eliminate manual math and measurements
Common Applications
Residential Stairs: Homeowners and contractors planning new interior or exterior stairs use this calculator to determine proper stair dimensions. Standard residential stairs use 7.5-inch risers and 10-inch treads, which this calculator helps determine accurately.
Deck Stairs: Contractors and homeowners planning deck stairs use this tool to estimate stair dimensions needed. Deck stairs typically use similar dimensions to interior stairs but may have deeper treads for exterior use.
Basement Stairs: Builders and homeowners planning basement or cellar stairs use this calculator to determine stair dimensions needed, ensuring safe and code-compliant stairs.
Tips for Best Results
- Riser Height: Standard is 7.5 inches (comfortable); maximum is 8 inches (building code); minimum is 6 inches
- Tread Depth: Standard is 10 inches (comfortable); minimum is 9 inches (building code); deeper (11-12") is more comfortable
- Rise + Run: Should be between 17-18 inches for comfortable stairs (building code guideline)
- Stair Width: Standard is 36 inches; minimum is 30 inches (building code); wider (42-48") is more comfortable
- Check Building Codes: Always verify local building codes for specific requirements and permit needs
Frequently Asked Questions
How many steps do I need for a 96 inch total rise?
For a 96-inch total rise with standard 7.5-inch risers, you'll need 13 risers (which means 12 steps/treads). The calculator will adjust the riser height slightly (to 7.38 inches) to fit evenly. Total run will be about 120 inches (10 feet) with 10-inch treads.
What's the standard riser height for stairs?
Standard riser height is 7.5 inches (comfortable and safe). Building codes allow 6-8 inches for riser height. Maximum is 8 inches. Minimum is 6 inches. The calculator ensures all risers are uniform for safety.
What's the minimum tread depth?
Minimum tread depth is 9 inches (building code). Standard is 10 inches (comfortable). Deeper treads (11-12 inches) are more comfortable but take more space. The calculator helps balance comfort and space constraints.
How long should my stringer boards be?
Stringer length is calculated using the Pythagorean theorem: √(Total Run² + Total Rise²). For a 96-inch rise with 120-inch run, stringer length is approximately 154 inches (12.8 feet). Add extra length for cutting and waste.
What does "rise + run" mean?
Rise + Run is the sum of individual riser height and tread depth. Building codes recommend this sum should be between 17-18 inches for comfortable and safe stairs. For example, 7.5" riser + 10" tread = 17.5" (within code).
Do I need a permit for building stairs?
Many areas require permits for new stairs, especially exterior stairs or structural changes. Check local building codes for permit requirements. Always ensure stairs meet building code requirements for safety and compliance.