Concrete Beam Calculator — ft, yd³, rebar
How to use this calculator
Select beam type (rectangular, T-beam with slab flange, or L-beam edge). Enter width, total depth, and span length. For T/L-beams, add flange width and slab thickness. Results update instantly.
Cost — pick ready-mix per yd³, 80-lb bags, or 60-lb bags.
Reinforcement — bottom tension bars, top compression bars, and stirrups with variable spacing (closer at ends per ACI 318-19 §18.6.4). Min/max reinforcement ratios shown.
Labor — rate per beam, per yd³, or flat price.
Saved Calculations
| Time | Type | Size | Qty | Vol yd³ | Concrete $ | Rebar | Rebar $ | Labor | Total |
|---|
How to Calculate Concrete for Beams
This calculator estimates concrete volume, reinforcement, and cost for rectangular, T-beam, and L-beam sections. Enter width, depth, and span in feet and inches. For T/L-beams, specify flange width and slab thickness. Volume accounts for the beam stem only (flange is typically part of the slab pour).
Reinforcement per ACI 318-19
Bottom tension bars carry the bending moment. Top compression/continuity bars are required at supports. Stirrups resist shear — spaced at d/4 in plastic hinge zones and d/2 in critical zones near supports, with wider spacing at midspan per ACI 318-19 §18.6.4. Minimum reinforcement ratio: 3√(f'c)/fy but not less than 200/fy (§9.6.1).
Formulas
Rectangular: V = b × h × L. T-beam: V = b_w × h × L + (b_f − b_w) × h_f × L (stem + flange). L-beam: V = b_w × h × L + (b_f − b_w) × h_f × L (one-sided flange). Weight: 150 lb/ft³. Stirrup perimeter: 2×(b_w − 2×cover) + 2×(h − 2×cover) + 2×hook.
FAQ
What is the typical beam depth? Rule of thumb: span/16 to span/12 for simply supported beams. A 20 ft span typically needs 15–20 inch deep beam. Should I include the flange volume? The flange (slab) is usually poured with the slab — this calculator includes it in the total for material ordering.
