Baluster layout guide · 5 min read
How to calculate equal baluster spacing
Calculate an equal clear gap, baluster count, and repeatable centre-to-centre layout between posts.
Measure the clear opening
Measure between the finished inside faces of the posts or boundaries that contain the balusters. Do not use the outside-to-outside rail length. Check the opening at the actual baluster line because posts and rails are not always perfectly parallel.
Find a count that respects the maximum gap
For a chosen number of balusters, subtract their combined width from the clear opening. Divide what remains by the number of spaces, which is one more than the baluster count when equal end gaps are used.
Equal gap = (opening − baluster count × baluster width) ÷ (baluster count + 1)
Treat the permitted opening as a hard maximum, not a target. Verify the rule and measurement method that apply to your guard or railing.
Mark centres instead of chasing every gap
Once the equal gap is known, add one baluster width to get the repeatable centre-to-centre spacing. The first centre is one gap plus half a baluster width from the inside face of the starting post.
On-centre spacing = equal gap + baluster width First centre = equal gap + ½ baluster width