How this calculator works
It converts your railing length to inches and divides by the on-center spacing to find how many balusters fit along the run.
Worked example — a 16 ft railing at 4.5 in on center:
192 in ÷ 4.5 = 43 balusters.
192 in ÷ 4.5 = 43 balusters.
Mind the 4-inch rule
Most codes require that a 4-inch sphere cannot pass between balusters, so the gap must stay under 4 inches. Tighter spacing means more balusters.
Frequently asked questions
How far apart should balusters be?
Close enough that a 4-inch ball can’t pass through — usually about 4 to 4.5 inches on center.
How many balusters per foot?
Roughly 2.5–3 per foot at standard spacing.