About this calculator
Divide a run into equal gaps, for fence posts, joists, balusters, shelves or tiles, and get every centre mark to hook your tape on.
How it’s calculated
Gap = (length − items × width) ÷ number of gaps. There is one more gap than items, or one fewer if items sit at both ends.
Worked example
With these inputs:
- Total length
- 3000 mm
- Item width
- 90 mm
- Set by
- Number of items
- Number of items
- 6
- Items at both ends
- No
the result is:
- Gap between items
- 351 mm
- On-centre spacing
- 441 mm
- Centre marks from start (mm)
- 396, 838, 1,279, 1,721, 2,162, 2,604
Tips from the trade
- Mark from one end only, so errors don’t add up.
Results are estimates for planning and pricing. Check quantities against your drawings, the manufacturer’s data and the Building Regulations before ordering.