Total Balusters
48
Posts
5
Rail Length
42.5 ft
Est. Cost
$300
48
5
42.5 ft
$300
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Inputs
Result
Posts = ceil(20/6) + 1 = 4. Sections = 3. Balusters per section = floor((72 - 3.5) / (4 + 1.5)) = floor(68.5 / 5.5) = 12. Total = 12 × 3 = 36 balusters. Rail = 20 + (4 × 0.25) = 21 ft. Cost = 20 × $15 = $300.
Inputs
Result
Posts = ceil(40/6) + 1 = 8. Sections = 7. Balusters per section = 12. Total = 12 × 7 = 84. Rail = 40 + (8 × 0.25) = 42 ft. Cost = 40 × $25 = $1,000.
With standard 4-inch spacing and 1.5-inch balusters, you need about 2-3 balusters per foot of railing. The exact count depends on post spacing: for 6-foot sections, you need about 12 balusters per section.
| Baluster Spacing | Per Foot | Per 6-ft Section | Per 8-ft Section |
|---|---|---|---|
| 3.5" (tight) | 2.4 | 14 | 19 |
| 4.0" (code max) | 2.2 | 12 | 17 |
| 3.75" (common) | 2.3 | 13 | 18 |
Building code requires that a 4-inch sphere cannot pass between balusters. This means the clear space between balusters must be less than 4 inches. Most builders use 3.5 to 4 inch spacing to meet code.
Railing posts should be spaced no more than 6 to 8 feet apart for structural stability. Many builders prefer 6-foot spacing for a stronger railing. Always place posts at corners and ends.
| Post Spacing | Rail Stiffness | Posts for 24 ft Run | Best For |
|---|---|---|---|
| 4 ft | Very rigid | 7 posts | Cable railing, glass panels |
| 6 ft | Solid | 5 posts | Wood & composite (most popular) |
| 8 ft | Some flex | 4 posts | Metal railing, fewer posts |
Residential deck railing must be at least 36 inches high per IRC code. For decks more than 30 inches above grade, some jurisdictions require 42-inch railings. Always check local building codes.
| Scenario | Minimum Height | Code Reference |
|---|---|---|
| Deck ≤ 30" above grade | 36" | IRC R312.1.1 |
| Deck > 30" above grade | 36–42" | Varies by jurisdiction |
| Commercial balcony | 42" | IBC 1015.3 |
| Stair handrail | 34–38" | IRC R311.7.8 |
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Last Updated: Oct 19, 2026
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