Craft & Making
Board Spacing Calculator
Enter span, board width and gap (or board count) to see layout.
Even board spacing
Decking, cladding and slatted screens look even when board width and gap pack consistently across a clear span. With a target gap, the tool estimates how many boards fit using floor((span + gap) ÷ (board + gap)), then redistributes any leftover length into the actual gap so the run finishes flush. Alternatively, set a target board count (≥2) and it solves the gap from the leftover space. Always check manufacturer expansion gaps for composites — they can override a purely aesthetic spacing. Related layout tools include the fence post calculator for post centres and the decking quantity estimator for board metres.
Worked example
A 240 cm span with 14 cm boards and a 0.5 cm target gap fits floor((240.5)/(14.5)) = 16 boards; leftover length redistributes to an actual gap of about 1.07 cm between boards.
Limits and assumptions
Clear span between posts or walls only. Picture-frame borders, miters and composite expansion minimums are not enforced — check the product data sheet.
Frequently asked questions
Should I lock gap or board count?
Lock gap when the manufacturer specifies a minimum; lock count when you already bought a fixed number of boards.
Why is actual gap larger than my target?
Whole boards only. Leftover millimetres are shared across gaps so the run meets both ends.
Do end gaps count?
This layout assumes boards fill edge to edge with gaps only between boards. Add end clearances in the span if required.
Is this a structural calculator?
No — it spaces boards visually. Joist centres and fixings follow separate span tables.