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Baluster spacing calculator

Lay out level or stair rails, then measure every centre from the same post.

01

Your railing

Rail type

Measure the bay

in
Measure inside face to inside face at the baluster line.
in
Measured horizontally.
in
Your horizontal layout target.
At the posts
0 uses the minimum count. Add more for tighter gaps and fitting room.
02

Your spacing layout

Balusters per bay13Minimum for your target
Horizontal clear gap3.750 in≈ 3 3/4 in · 14 equal spaces

Target: 4.000 in

Level rail · equal end gaps0.0°
Rail elevation
100%

Drag to pan · pinch or Ctrl + wheel to zoom

72 inBetween post faces, along rail

Spacing and slope to scale. Heights and connections are schematic.

01 · First centre4 1/2 inAlong rail from the starting post face
Centre to centre5 1/4 inAlong rail · use cumulative marks below
Clear gap along rail3 3/4 inSame as the horizontal gap
Horizontal opening72 inBetween the inside faces of the posts
Centre-mark schedule13 marks · along rail

Start at the lower post on stairs, or either post on a level rail. Measure every mark from that same inside face. The first baluster is highlighted in the drawing.

  1. 01
    4 1/2 in4.500 in
  2. 02
    9 3/4 in9.750 in
  3. 03
    15 in15.000 in
  4. 04
    20 1/4 in20.250 in
  5. 05
    25 1/2 in25.500 in
  6. 06
    30 3/4 in30.750 in
  7. 07
    36 in36.000 in
  8. 08
    41 1/4 in41.250 in
  9. 09
    46 1/2 in46.500 in
  10. 10
    51 3/4 in51.750 in
  11. 11
    57 in57.000 in
  12. 12
    62 1/4 in62.250 in
  13. 13
    67 1/2 in67.500 in

Fractions are rounded to 1/16 in. Check both end gaps before fastening. Do not repeatedly add rounded spacing.

One straight bay, equal end gaps

Actual baluster width: 1.500 in horizontally. Balusters and posts stay plumb; centre marks are measured along the rail. Rail height, baluster cut lengths and connections are separate design decisions.

Fast field layout

One post.
Every mark.

Need the complete stair layout? →

Measure the actual bay

Measure between the inside faces of installed posts. For stairs, choose whether your measurement runs along the rail or horizontally; the calculator converts it to the layout line.

Match the slope

Enter the measured angle or use one finished riser and one tread run. The run excludes nosing. Use the actual rail angle if it differs from the stair pitch.

Transfer every centre from one post

Use the numbered schedule along the rail, starting at the lower post on stairs. Keep the balusters plumb and transfer centres vertically to a parallel second rail. Dry-fit the first and last baluster before fastening the rest.

Maximum gap is not the whole guard design.

Confirm the opening limit, guard height, baluster strength, climbability, rail spans, post connections and fastening requirements that apply to the location and occupancy. Measure the real opening and verify the completed guard before use.

Baluster field guides

Lay out equal spaces without accumulated error.

Use the actual opening and baluster width, then transfer repeatable centre marks from one reliable datum.

Space stair balusters

Understand why a level-rail spacing layout cannot simply be copied onto a stair, and how plumb balusters change measurements along the slope.

Read guide

Calculate equal spacing

Choose equal end gaps or balusters tight to the posts by appearance and fitting detail, then divide the opening without creating an oversized gap.

Read guide

Mark balusters accurately

Understand why cumulative marks prevent a drifting layout, when a spacer is useful, and how to keep rounded measurements from collecting at one end.

Read guide

Space stair balusters

Choose a consistent horizontal or along-rail measuring method, and understand why the rail angle and actual plumb-member width change the layout.

Read guide