🪵 Baluster Calculator
Work out how many balusters you need for a deck or porch railing, and the actual spacing between them, based on the maximum gap allowed.
What this calculator does
The baluster calculator finds how many balusters (the vertical spindles in a deck or stair railing) you need to fill a given railing length without exceeding a maximum allowed gap.
The formula
The calculator converts your railing length to inches, then finds the smallest number of balusters whose combined width plus even gaps fits the run without any gap exceeding your maximum. Most U.S. residential codes require gaps no wider than 4 inches so a small child or pet cannot pass through. The actual, evenly-distributed gap is shown alongside the baluster count.
This is a general planning estimate. Always confirm the exact maximum gap and post spacing rules required by your local building code before ordering materials.