Stair Stringer Calculator
Calculate stair rise, run, and stringer dimensions. Get code-compliant measurements for safe, comfortable stairs.
How to Use This Calculator
Building code-compliant stairs requires precise calculations. This calculator determines the exact rise and run for each step based on your total height change and available space.
- Measure total rise: the vertical distance from lower floor to upper floor surface.
- Measure total run: the horizontal distance available for the stairs.
- Enter the stair width (36 inches minimum for most residential codes).
- Specify tread thickness if using standard lumber or decking.
- Review results for code compliance and adjust if needed.
Why This Matters
Stair safety depends on consistent rise and run dimensions. Uneven steps are a leading cause of falls. Building codes establish strict limits on riser height (max 7.75 inches) and tread depth (min 10 inches) to ensure safe, comfortable stairs. Proper stringer layout is essential for structural integrity.
- Calculate code-compliant rise and run
- Determine number of stringers needed
- Get exact stringer cutting dimensions
- Verify comfort rule compliance
- Plan lumber and material quantities
Worked Examples
Standard Deck Stairs
Deck 32 inches above ground with 48 inches of available run space.
Basement Stairs
96 inches (8 feet) floor-to-floor rise with 10 feet of run available.
Tight Space Stairs
36 inch rise with only 36 inches of run available.
Common Mistakes to Avoid
- Not accounting for tread thickness when measuring total rise - measure from finished floor to finished floor.
- Inconsistent rise heights - all risers must be within 3/8 inch of each other.
- Forgetting the bottom riser adjustment - cut bottom of stringer by tread thickness.
- Using undersized stringers - must maintain 3.5 inches of wood after notches.
- Not enough stringers - bounce and tread deflection indicate too few stringers.