calcs.homes
calcs.homes
Enter your railing's total length, baluster width, and the maximum code-allowed gap to get an exact baluster count and evenly split spacing.
Estimate only — check your local code's exact max-gap requirement before building.
We solve for the smallest baluster count where n balusters plus (n+1) gaps fit the rail length without any gap exceeding your max — n = the ceiling of (length − max gap) ÷ (baluster width + max gap) — then recompute the actual gap as (length − n × baluster width) ÷ (n + 1), splitting the leftover space evenly across every gap from end to end.
Codes cap the gap — commonly under 4 in, sized so a 4 in sphere can't pass through — to keep young children from squeezing through the railing or getting a head caught between balusters. Rounding the baluster count up and re-splitting the leftover space evenly keeps every single gap at or under that limit, rather than crowding one end and leaving slack at the other; inspectors measure the actual built gap, not the target number on a plan.
Most US residential codes require gaps small enough that a 4 in sphere can't pass through — check your local building department, since some jurisdictions use a stricter standard.
Real-world railings rarely divide evenly into whole 4 in gaps, and inspectors check the actual built gap — spacing slightly under 4 in and splitting evenly avoids failing inspection over a fraction of an inch.