About this calculator
Equal spacing for spindles that keeps every gap under the 100 mm rule, with the first-centre measurement for marking out.
How it’s calculated
Count = ceil((length − max gap) ÷ (baluster width + max gap)). Actual gap = (length − count × width) ÷ (count + 1).
Worked example
With these inputs:
- Rail length between posts
- 1800 mm
- Baluster width
- 41 mm
- Maximum gap
- 99 mm
- Number of sections
- 4
the result is:
- Balusters per section
- 13
- On-centre spacing
- 132 mm
- First baluster centre from post
- 111 mm
- Total balusters
- 52
Tips from the trade
- Set your maximum a little under the limit, because timber moves. 3⅞" or 95 mm is safer.
- Make a spacer block cut to the gap and use it on every baluster.
Results are estimates for planning and pricing. Check quantities against your drawings, the manufacturer’s data and the Building Regulations before ordering.