Spindle Spacing Calculator

Your details

Stair railings run on an angle, so the on-slope distance between spindles differs from the horizontal gap.
The clear span between the inner faces of the two end posts.
in
The face width of each spindle or baluster. Standard square balusters are 1.5 in (3.8 cm).
in
U.S. and Canadian building codes require this gap to be no more than 4 in (10 cm) so a 4-inch sphere cannot pass through.
in
Balanced end spacing adjusts the first and last gap so spindles appear centered in the opening. Even spacing uses the same gap between every spindle and at both ends.
Spindles neededCode compliant
17

Total number of spindles for this railing run

Gap between spindles4
End gap (at posts)3.25
On-center spacing5.5
Code complianceCompliant - largest gap is 4.00 in (max 4 in)
4 in
Too tight<2Code safe2-4Too wide4+

17 spindles, 4.00 in apart.

  • You need 17 spindles for this railing run.
  • Interior gaps are 4.00 in and end gaps are 3.25 in.
  • Set your drill or jig to 5.500 in on-center between spindles.

Next stepLay out the first spindle at the calculated end spacing from the post, then step across at the on-center distance.

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