Baluster Calculator
Count evenly spaced balusters from an opening, baluster width and permitted clear gap.
Last reviewed September 19, 2026
Result
Buy 22 balustersEstimate
No cutting allowance is included. The result is the installed count; add spares separately if the material is fragile or colour-matched.
- Balusters per opening
- 22
- Even clear gap
- 3.783 in
https://calcgallery.com/decking-fencing/baluster-calculator/
Results are estimates for planning only. Actual needs vary with site conditions, products and workmanship. Always confirm quantities with your supplier and follow local building codes and manufacturer instructions. Read the full disclaimer
How to use it
- Measure the clear distance between the inside faces of the posts or newels.
- Enter how many openings have that same clear length.
- Enter the actual baluster width and the maximum clear gap from the project requirements.
- Read the baluster count and the equal clear spacing to set out.
How it is calculated
The formula finds the smallest whole count whose equal spaces do not exceed the maximum you entered:
Balusters = ceil((opening − maximum gap) ÷ (width + maximum gap))
Actual gap = (opening − balusters × width) ÷ (balusters + 1)The result is then multiplied by the number of identical openings.
Set-out and safety
The gap is an input, not a recommendation. Guard and stair requirements vary. Use a project drawing, designer or applicable local rules to choose it.
Measure the clear opening. Do not use an outside-to-outside post dimension. Small errors accumulate across many spaces.
Mark from a common reference. Repeatedly measuring from the previous mark compounds error. A story pole or full-length tape layout keeps the final space consistent.
Check the real stock. Painted, turned and nominal balusters may not match their advertised width. Measure several pieces before final set-out.
With your numbers
- 22 balusters keep every clear gap at or below 4 in
- Even clear gap = (opening − baluster widths) ÷ spaces = 3.783 in
- 22 per opening × 1 openings = 22 balusters
Quick reference
No cutting allowance is included. The result is the installed count; add spares separately if the material is fragile or colour-matched.
| Job | Balusters to install |
|---|---|
| 10 ft opening, 1.5 in balusters | 22 |
| 6 ft opening, 1.5 in balusters | 13 |
| Three 6 ft openings | 39 |
| 8 ft opening, 2 in balusters | 16 |
| 3 m opening, 40 mm balusters | 21 |
| Two 2 m openings | 28 |
Common questions
- How many 1.5 inch balusters fit a 10 foot opening?
- With a user-supplied 4 in maximum clear gap, 22 balusters create 23 equal gaps of about 3.783 in.
- Does the calculator choose a code-compliant gap?
- No. Rules differ by location, building type and railing position. Enter the maximum from the approved drawing or the rules that apply to your project.
- Why are there one more spaces than balusters?
- A clear opening has a space at both ends as well as between each pair. Twenty-two balusters therefore make twenty-three equal spaces.
- Can I use this for stair balusters?
- Only when the entered opening and baluster widths are measured along the same set-out line. Sloped rails require careful project-specific measurement.