Run length and post spacing (same units)—posts if both ends need a post: floor(L/s)+1.
Both length and spacing must be positive. The model counts posts at both ends of the run: ⌊L ÷ s⌋ + 1. This matches the classic “fence‑post” interval counting when posts sit on every segment boundary including the last endpoint.
This calculator uses plain decimal numbers. If a result looks wrong, check whether you used a comma instead of a dot (or vice versa) where the field expects one.