Handrail & Baluster API

Railing and baluster layout maths as an API, computed locally and deterministically — the baluster-count, spacing and post numbers a deck builder, fabricator or balustrade designer sets a guardrail out with. The baluster-count endpoint gives the smallest number of balusters that keeps every gap within the safety limit: between two posts n balusters leave n+1 gaps, so the count = ceil((rail length − max gap) ÷ (baluster width + max gap)). The usual guardrail limit is a 100 mm (4-inch) sphere — a child-safety rule — so a 2000 mm rail with 40 mm balusters needs 14 of them at even 96 mm gaps; round up, because one fewer opens the gaps past the limit. The layout endpoint sets out a known count evenly: the gap = (rail length − total baluster width) ÷ (count + 1), the centre-to-centre pitch = baluster width + gap, and the first baluster's centre sits one gap plus half a baluster from the post face, so you mark the first centre and step off the pitch with the last gap landing equal to the first. The post-count endpoint sizes the frame: a run needs one more post than spans, spans = ceil(run ÷ max post spacing), posts = spans + 1, even spacing = run ÷ spans — a 6 m run at a 1.8 m max takes 4 spans and 5 posts at a tidy 1.5 m. Everything is computed locally and deterministically, so it is instant and private. Ideal for deck and balustrade design tools, fabrication and estimating apps, and building calculators. Pure local computation — no key, no third-party service, instant. Uses the common 100 mm infill rule — confirm your local code. 3 compute endpoints. For stair rise and run use a stair API; for fence pickets a fence API.