Concrete Beam Calculator

Calculator built by BuilderToolkits | Updated February 2026

Estimate concrete beam volume using length, width, height, and waste factor. This concrete beam calculator outputs cubic yards, cubic feet, and 80‑lb bag counts for quick takeoffs. For slab pours, the Concrete Slab Calculator is a fast cross-check. For reinforcement and subbase planning, use the rebar estimator and the gravel base calculator.

Inputs

Results

Concrete volume
0.81 yd³
22 ft³ total
Includes 10% waste.
80-lb bags (rough)
37 bags
Assumes ~0.6 ft³ yield per 80-lb bag (varies by mix).

Assumptions

  • Beam is a straight, rectangular section with uniform dimensions.
  • Waste factor covers form loss, spillage, and over-excavation.
  • 80-lb bag yield is an approximation; verify product labels.

Next Steps

✓Round up to the nearest 0.25 yd³ for ready-mix orders.
✓Estimate reinforcement with the rebar estimator.
✓For slab or pad volumes, use the concrete slab calculator.

Example

A 20 ft × 1 ft × 1 ft beam with 10% waste needs about 0.81 yd³ of concrete.

How to Calculate a Concrete Beam (Formula)

Volume (ft³): Length (ft) × Width (ft) × Height (ft)

Cubic yards: Volume (ft³) ÷ 27 × (1 + Waste %)

FAQ

What is a grade beam?

A grade beam is a reinforced concrete beam at or near ground level that supports walls or columns and spreads loads to the soil, often tying piers or footings together.

How much rebar in a concrete beam?

Rebar size and spacing depend on span, loads, and soil conditions. Start with the rebar estimator for quantity planning, then confirm spacing and bar size with local code or a structural engineer.

How deep should a beam be?

Beam depth depends on structural loads and span. Many residential grade beams are 12–24 inches deep, but depth should be verified by design requirements or engineering.

Difference between beam and footing?

Footings spread vertical loads into soil, while beams span between supports and carry loads along their length. Some systems combine both, but they serve different structural roles and require proper base preparation—see the gravel base calculator for subbase planning.

PSI for structural beams?

Many structural beams use 3,000–4,000 PSI concrete, but required strength depends on design and local code. For small pours, use the concrete bag calculator to estimate bag counts.

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