Stair Rise and Run Calculator | Free Construction Calculators
Calculate precise stair rise and run dimensions that comply with building codes and ergonomic standards. Our professional stair rise and run calculator helps contractors, builders, architects, and DIY homeowners design safe, comfortable stairs by determining the optimal number of steps, individual riser heights, and tread depths based on total vertical rise. Get instant calculations for residential and commercial staircases that meet IRC, IBC, and OSHA requirements. Perfect for interior stairs, exterior stairs, deck stairs, basement stairs, and multi-story construction projects. Ensure code compliance, occupant safety, and comfortable climbing with accurate rise and run calculations.
Code Compliant
Calculations follow IRC, IBC, and OSHA requirements for safe stair design
Ergonomic Design
Optimal rise and run ratios ensure comfortable and safe stair climbing
Professional Results
Precise measurements used by architects and professional stair builders
How to Use This Calculator
- Measure the total rise from finished floor to finished floor in inches (vertical height)
- Enter your desired rise per step (7.5 inches is ideal for residential stairs)
- Enter the tread run depth (10-11 inches is standard for residential)
- Click Calculate to see the number of steps and exact dimensions
- Verify that results meet your local building code requirements
- Adjust rise or run values if needed to optimize comfort and code compliance
Calculation Formula
Number of risers: Total Rise ÷ Desired Rise per Step (rounded to nearest whole number)
Actual rise per step: Total Rise ÷ Number of Risers
Number of treads: Number of Risers - 1
Total run: Number of Treads × Tread Run Depth
Stair angle: arctan(Total Rise ÷ Total Run)
About Stair Rise and Run Calculations
Stair rise and run are the fundamental measurements for designing safe, comfortable, and code-compliant stairs. The rise is the vertical height of each step (from top of one tread to top of the next), while the run is the horizontal depth of each tread (the part you step on). Proper stair design requires precise calculations to ensure consistent step dimensions, comfortable climbing, and compliance with building codes that govern residential and commercial construction.
Building codes strictly regulate stair dimensions for safety. The International Residential Code (IRC) requires maximum riser height of 7.75 inches, minimum tread depth of 10 inches, and maximum variation of 3/8 inch between any two risers in a stairway. The International Building Code (IBC) for commercial buildings requires maximum 7-inch rise and minimum 11-inch run. These requirements exist because inconsistent stair dimensions are a leading cause of falls and injuries. Even small variations in rise height can cause stumbling.
The ideal stair design follows the formula: 2 × Rise + Run = 24-25 inches. This ergonomic rule, based on average human stride length, creates comfortable stairs that feel natural to climb. For example, a 7.5-inch rise with 10-inch run equals 25 inches (2 × 7.5 + 10 = 25), which is ideal for residential applications. Steeper stairs (higher rise, shorter run) are more tiring and dangerous, while shallower stairs (lower rise, longer run) waste space and feel awkward. Professional stair builders use this calculator to optimize both safety and comfort while meeting code requirements.
Building Code Requirements (IRC/IBC)
Residential Stairs (IRC):
- Maximum rise: 7.75 inches (7 ¾ inches)
- Minimum run: 10 inches
- Minimum stair width: 36 inches
- Maximum riser variation: 3/8 inch between any two risers
- Minimum headroom: 6 feet 8 inches (80 inches)
Commercial Stairs (IBC):
- Maximum rise: 7 inches
- Minimum run: 11 inches
- Minimum stair width: 44 inches (48 inches for occupancy > 50)
- Maximum riser variation: 3/8 inch
- Minimum headroom: 6 feet 8 inches (80 inches)
Frequently Asked Questions
What is the ideal rise and run for residential stairs?
The ideal residential stair has a 7 to 7.5-inch rise and 10 to 11-inch run. This configuration follows the 2R + T = 24-25 inch rule (where R = rise and T = tread), which matches average human stride length and creates the most comfortable climbing experience. A 7.5-inch rise with 10-inch run (2 × 7.5 + 10 = 25) is considered perfect for most homes. Avoid exceeding 7.75 inches rise or going below 10 inches run, as these are IRC code maximums/minimums designed for safety.
How do I calculate the number of steps needed for my stairs?
Divide your total rise (floor-to-floor height) by your desired rise per step, then round to the nearest whole number. For example, if your total rise is 108 inches and you want 7.5-inch risers: 108 ÷ 7.5 = 14.4, which rounds to 14 risers. Then calculate the actual rise: 108 ÷ 14 = 7.714 inches per step. Remember that the number of treads is always one less than the number of risers because the top floor serves as the final landing.
Why must all stair risers be exactly the same height?
Building codes require all risers to be within 3/8 inch of each other because inconsistent step heights are a major cause of falls. When climbing stairs, people develop a rhythm and muscle memory based on the first few steps. If one step is even slightly different, it disrupts this rhythm and can cause stumbling, especially when descending in low light or carrying items. Consistent riser heights are critical for safety, which is why professional builders use precise calculations and verify measurements during construction.
What is total run and how much space do I need for my staircase?
Total run is the horizontal distance the staircase travels from bottom to top (not including landings). Calculate it by multiplying the number of treads by the tread depth. For example, 13 treads at 10 inches each = 130 inches (10 feet 10 inches) of total run. Add space for top and bottom landings (minimum 36 inches each per code) to determine total floor space needed. A typical residential staircase with 14 risers and 10-inch treads requires approximately 11-12 feet of total horizontal space including landings.
Can I use steeper stairs to save space?
While it's tempting to use steeper stairs (higher rise, shorter run) to save floor space, this creates safety hazards and violates building codes. Maximum rise of 7.75 inches (IRC) or 7 inches (IBC) cannot be exceeded. Steeper stairs are tiring to climb, dangerous to descend, difficult for elderly or disabled users, and won't pass inspection. For tight spaces, consider alternating tread stairs (paddle stairs), spiral stairs, or ship's ladders, which have different code requirements and are appropriate for specific applications like attics or lofts.
Related Stair Calculators
Professional Stair Building Tips
- Verify total rise: Measure from finished floor to finished floor, accounting for flooring thickness
- Use story poles: Create a measuring stick marked with riser heights to ensure consistency during construction
- Check local codes: Some jurisdictions have stricter requirements than IRC/IBC minimums
- Consider handrails: Codes require handrails on one side (residential) or both sides (commercial) for stairs with 4+ risers
- Account for nosing: Tread nosing (overhang) of 0.75-1.25 inches improves foot placement and comfort
- Plan for headroom: Maintain 6'8" minimum clearance throughout the stair run, measured vertically from tread nosing
- Use quality materials: Stair stringers should be 2×12 lumber minimum for residential applications
- Test before building: Walk through the calculations mentally or create a mockup for critical projects