Baluster Calculator
Use our baluster calculator to estimate how many balusters (spindles) you need for a railing. Enter railing length, number of posts, post width, baluster width, and desired spacing to get balusters needed. Includes a simple baluster spacing formula and FAQs on how far apart balusters should be.
Balusters and Spindles
Balusters are the vertical pieces that fill the space between a top rail and bottom rail (or deck surface). Many people also call them spindles.
A baluster calculator helps you estimate how many balusters you need based on your railing length, post layout, baluster width, and the spacing you want between balusters.
Spacing rules can vary by location and application. If you are building a guardrail, always check local code requirements before finalizing your spacing.
Baluster Spacing Formula
This calculator estimates balusters per span (between posts) and multiplies by the number of spans.
Convert feet to inches so all dimensions match.
If posts are 2 or more, spans are the spaces between posts. If posts is 1, treat it as one span for estimation.
Assumes the given railing length includes the posts.
Assumes spans are equal length.
Uses the layout: space + baluster + space + ... + baluster + space.
Rounded down to a whole number.
How to Calculate Balusters Needed
- 1
Enter the railing length (ft).
- 2
Enter the number of posts and the post width (in).
- 3
Enter the baluster width (in).
- 4
Enter the baluster spacing (in).
Frequently Asked Questions
In most railing contexts, yes. Spindle is a common term for a baluster, especially in residential projects.
It depends on local building code and whether it is a guardrail. Many guardrail rules limit the maximum clear spacing, so check your local requirements before deciding.
It depends on your clear span length, your baluster width, and the spacing you choose. This calculator estimates how many will fit while keeping spacing consistent across spans.
There is no single fixed number because it depends on baluster width and spacing. As spacing gets smaller or balusters get thinner, the count per foot increases.
A common approach is to solve for how many balusters fit in a span, then back-calculate spacing so the gaps are even. This calculator assumes you choose the spacing and returns how many balusters fit.