Spindle Spacing Calculator
Calculate optimal spacing for deck and stair railing spindles with building code compliance
Calculate Spindle Spacing
Application Type
Spacing Method
Railing Measurements
Distance between posts or walls where spindles will be installed
Building code typically requires 4 inches (10 cm) maximum
Cost Calculation (Optional)
Spindle Spacing Results
Spacing meets the 4-inch maximum requirement for child safety.
Unit Length: Spindle width (0.00") + Max spacing (4.00") = 4.00"
Number of Spindles: 0.0" ÷ 4.00" = 0 spindles
Even Spacing Formula: (0.0" - 0 × 0.00") ÷ 1 = 0.000"
Installation Guidelines
Example Calculation
Deck Railing Project
Project: 8-foot deck railing section
Inside distance: 75 cm (between posts)
Spindle width: 2 cm
Max spacing: 10 cm (4 inches)
Calculation Results
Unit length = 2 cm + 10 cm = 12 cm
Number of spindles = 75 cm ÷ 12 cm = 6.25 → 6 spindles
Total spindle width = 6 × 2 cm = 12 cm
Available space = 75 cm - 12 cm = 63 cm
Even spacing = 63 cm ÷ 7 spaces = 9.0 cm
End spacing (centered) = (75 - 6×12 + 10) ÷ 2 = 6.5 cm
Final result: 6 spindles with 9.0 cm even spacing or 6.5 cm end spacing
Building Code Requirements
Spacing Methods
Installation Tips
Measure inside distance between posts accurately
Mark all spindle locations before drilling
Use a 4-inch ball to test spacing compliance
Use a story pole for consistent spacing
Pre-drill to prevent wood splitting
Check local codes before installation
Understanding Spindle Spacing Calculations
What are Spindles?
Spindles (also called balusters) are vertical support members that create a safety barrier for railings on decks, stairs, and balconies. They prevent people, especially children, from falling through the railing while maintaining visibility.
Building Code Requirements
- •Maximum 4-inch (10 cm) spacing between spindles
- •Designed to prevent child head entrapment
- •36-inch minimum railing height
- •Must withstand 200 lb load per linear foot
Calculation Methods
1. Unit Length: Spindle Width + Max Spacing
2. Number of Spindles: Distance ÷ Unit Length (rounded down)
3. Even Spacing: (Distance - Total Spindle Width) ÷ (Spindles + 1)
4. End Spacing: (Distance - Spindles × Unit Length + Max Spacing) ÷ 2
Slanted Spacing
For stairs, spacing along the slanted rail is calculated using:
Slanted Spacing = Horizontal Spacing ÷ cos(angle)
Where angle = arctan(rise ÷ run)