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Beam Size Calculator
Preliminary RCC beam size from span and support condition: minimum depth per ACI 318 Table 9.3.1.1, suggested width and drop below the slab.
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About this calculator
Get a starting size for an RCC beam from its span and supports — the minimum depth that controls deflection, a practical width and how far it drops below the slab.
How it's calculated
- h,min = L/16 (simply supported), L/18.5 (one end continuous), L/21 (both ends), L/8 (cantilever)
- For Grade 40 steel multiply by 0.4 + fy/100,000 = 0.8
- Width ≈ 0.45 × depth, not less than the wall thickness
What size beam for a 15 ft span?
About 9″ × 12″ minimum for a typical house beam with one end continuous; heavy wall or tank loads need a bigger section.
Results are calculated from the values you enter using standard formulas. Download the PDF to keep a record. For certified testing, design or construction, talk to our engineers.
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