Deck Railing Calculator
Railing posts, balusters and rail length.
Enter your values
ⓘ Live results
Results
- Posts needed
- 11
- Rail sections
- 10
- Balusters per section
- 14
- Total balusters
- 140
Quick answer
Railing posts are spaced along the perimeter and balusters are spaced to meet the code maximum gap, usually 4 inches.
balusters per section = ceil((post spacing - baluster width)/(gap+width))
How to use the Deck Railing Calculator
- 1Measure the total railing perimeter and choose a post spacing (commonly 6 ft max).
- 2Enter baluster width and the maximum code gap, usually 4 inches so a sphere cannot pass.
- 3The calculator spaces balusters evenly within each section to meet the gap limit.
Worked example
Using the values the calculator loads with:
Inputs
- Railing perimeter60 ft
- Post spacing6 ft
- Baluster width1.5 in
- Max gap allowed4 in
Results
- Posts needed11
- Rail sections10
- Balusters per section14
- Total balusters140
Frequently asked questions
What is the standard baluster gap rule?
Most codes require gaps small enough that a 4-inch sphere cannot pass through.
Do corner posts count twice?
Enter true perimeter length; the calculator already adds one extra post for the closing corner.
About this calculator
- Built and reviewed by James Whitfield · How we build and test calculators
- Report an error
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.