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Baluster Spacing Guide: How Many Balusters Do I Need?
Plan on 3 balusters per foot, spaced about 4 inches on center, so no gap in your railing is wider than 4 inches. This guide shows how to measure your stairs and balcony, how many balusters to order, and how to space them evenly.
Want the math done for you? Our Baluster Spacing Calculator gives you the baluster count, your first mark and every mark after it, for a balcony or your stairs.
Quick Answer
| Where | Rule of thumb | Example |
|---|---|---|
| Balcony or landing | 3 balusters per foot | 20 ft balcony = 60 balusters |
| Stairs | 3 balusters per step (2 on some steep stairs) | 14 steps = 42 balusters |
| Stairs open on both sides | Count each side separately | 14 steps x 2 sides = 84 balusters |
Order a few extra balusters (about 5%) to cover cutting mistakes or a damaged piece.
How to Measure for Balusters
Tools you need: a tape measure and a pen.
Measuring a balcony or landing
- Measure the length of the railing in feet: wall to wall, newel post to newel post, or newel post to wall.
- Multiply the feet by 3. A 20-foot balcony needs about 60 balusters (20 x 3 = 60).
Measuring stairs
- Count the steps that will have a railing.
- Multiply by 3. Most treads hold 3 balusters. Some steep stairs with shallow treads use 2 balusters per step, or alternate 2 and 3, as long as no gap is over 4 inches.
- If your stair is open on both sides, count each side.
How to Space Balusters
Space your balusters about 4 inches on center, measured from the center of one baluster to the center of the next. That works out to 3 balusters per foot and keeps every gap under 4 inches.
On center is not the same as the gap. Code is about the open space between balusters, so a 1/2″ baluster at 4″ on center leaves a 3-1/2″ gap. That’s within code. If you use wider balusters or decorative styles, check the widest opening, including any openings inside the baluster’s design.
Tips for even spacing
- Uneven runs: if the length doesn’t divide evenly, split the difference so both ends match. For example, a 3″ gap at each end instead of 4″ at one end and 2″ at the other.
- Small treads or big overhangs: find the center of the usable tread space and work outward, fitting your balusters without going over a 4″ gap or hitting the tread above.
- Lay it out first: mark every baluster location in pencil before you drill a single hole.
Baluster Spacing and Building Code
Most U.S. building codes, based on the International Residential Code (IRC), require that a 4-inch sphere cannot pass through any opening in the railing. On the open side of a staircase, the IRC allows up to 4-3/8 inches. Local codes vary, so always check with your local building department before you install.
Baluster Spacing FAQ
How many balusters do I need per foot?
Plan on 3 balusters per foot. That spaces them about 4 inches on center and keeps the gaps under 4 inches.
How many balusters do I need per step?
Most stairs need 3 balusters per step. Some steep stairs with shallow treads use 2 per step, as long as no gap is over 4 inches.
What is the maximum gap between balusters?
Most codes say a 4-inch sphere can’t pass through any opening in the railing. The IRC allows 4-3/8 inches on the open side of stairs. Check your local code.
Is baluster spacing measured on center or between balusters?
Code is about the open gap between balusters. Most people lay them out about 4 inches on center, which leaves a gap under 4 inches with standard 1/2″ balusters.
Should I order extra balusters?
Yes. Order about 5% extra to cover cutting mistakes and any damaged pieces.