Baluster Calculator
Find how many balusters (spindles) you need for a staircase or deck and the exact gap between them, keeping under the 100 mm UK Building Regulations limit.
Enter your values and press Calculate.
How to use the Baluster calculator
For stairs and landings in homes, Approved Document K requires that a 100 mm sphere cannot pass through any opening. Work in the same unit throughout — the calculator also works in inches if you enter every measurement in inches.
Formula
Balusters = ⌈(length − max gap) ÷ (baluster width + max gap)⌉; gap = (length − n × width) ÷ (n + 1).
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