Baluster Calculator
How many balusters do you need? Enter the railing length and spacing.
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Railing length—
Estimated cost—
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How this calculator works
It converts your railing length to inches and divides by the on-center spacing to find how many balusters fit along the run.
Worked example — a 16 ft railing at 4.5 in on center:
192 in ÷ 4.5 = 43 balusters.
Mind the 4-inch rule
Most codes require that a 4-inch sphere cannot pass between balusters, so the gap must stay under 4 inches. Tighter spacing means more balusters.
Frequently asked questions
How far apart should balusters be?
Close enough that a 4-inch ball can’t pass through — usually about 4 to 4.5 inches on center.
How many balusters per foot?
Roughly 2.5–3 per foot at standard spacing.
Planning a decking project
Board dimensions are nominal sizes and can vary by product. Include joist layout, picture framing, stairs, fascia, seams, and the direction of the boards in a final takeoff. Structural sizing and ledger details should be checked against local code or reviewed by a qualified builder.
How to use this estimate
- Measure the project in the units shown and recheck your measurements before ordering.
- Use the waste allowance as a planning buffer, not as a substitute for a detailed material takeoff.
- Compare the result with the package yield, coverage, or weight listed by your supplier.
- Prices are user-entered estimates and may change by location, product, delivery, and season.
Accuracy and limitations
Calculapedia provides educational planning estimates. It does not inspect your site, select products, guarantee quantities, or replace a contractor, engineer, architect, building official, or supplier. Confirm the final quantity and any safety or code requirements before buying or building.