Stair Calculator

Professional-grade stair calculation tool for US construction. Get precise riser height, tread depth, and step count in seconds.

Error: Please check your input values.

Total Rise (Height)

Floor-to-floor height (Standard: 96-120 inches)

Total Run (Length)

Horizontal length of the stairway

Max Riser Height

inches

IRC Building Code Maximum: 7.75 inches

Min Tread Depth

inches

IRC Building Code Minimum: 10 inches

Your Stair Calculation Results

Number of Steps

Risers

Riser Height

7.71″

Per Step

Tread Depth

9.23″

Step Depth

Total Steps

Treads

Safety Note: Always verify calculations with local building codes before construction. The “7-11 Rule” (7″ riser × 11″ tread) is a common comfort guideline, but local regulations may vary.

📐 Stair Building Expert Notes & Reference Tables

Stair Building Code Cheat Sheet

Standard / Application	Max Riser Height	Min Tread Depth	Notes
IRC (Residential)	7.75 inches	10 inches	Most common US residential standard
IBC (Commercial)	7 inches	11 inches	Commercial & public buildings
ADA Accessibility	7 inches	11 inches	Americans with Disabilities Act
OSHA (Workplace)	9.5 inches	9.5 inches	Temporary/construction stairs
Best Practice (Comfort)	7.0 – 7.5 inches	10 – 11 inches	Optimal for daily use

Unit Conversion Reference

1 Foot = 12 Inches

1 Inch = 2.54 cm

1 Yard = 3 Feet

Feet	Inches	Common Application
8 ft	96 in	Standard ceiling height
9 ft	108 in	Common floor-to-floor height
10 ft	120 in	Luxury/residential floor height
12 ft	144 in	Commercial/warehouse
14 ft	168 in	Two-story/grand entry

Stair Calculation Formulas

Number of Risers = ceil(Total Rise ÷ Max Riser Height)

Always round UP for safety (Math.ceil in our calculator)

Actual Riser Height = Total Rise ÷ Number of Risers

Number of Treads = Number of Risers – 1

Tread Depth = Total Run ÷ Number of Treads

The “7-11” Comfort Rule

A commonly used guideline for comfortable stairs: Riser Height (inches) × Tread Depth (inches) ≈ 75. For example, 7″ riser × 10.7″ tread = 74.9″. This formula creates a natural, comfortable stride.

Pro Tips from Industry Experts

#1: Consistency is Critical

Variance in riser height should not exceed 3/8″ between any two steps. Inconsistent risers are a leading cause of stair-related accidents. Use a story pole or laser level to verify uniformity during installation.

#2: Headroom & Clearance Planning

Minimum headroom requirement is 6’8″ (80 inches) measured vertically from the stair tread nosing. For basement stairs, some local codes allow 6’4″ minimum. Always check your specific municipality’s requirements.

#3: The “Blondel” Formula Check

Verify your design with Blondel’s Formula: 2R + T = 25″ (where R = riser height, T = tread depth). Result should be between 24-26 inches. Example: 2×7″ + 10.5″ = 24.5″ (excellent).

#4: Order of Operations

1. Determine Total Rise (measure accurately).
2. Calculate Number of Risers (round UP).
3. Determine Actual Riser Height.
4. Calculate Tread Depth based on available run.
5. Verify against local building codes.

Free Stair Calculator: Steps, Rise & Run