Concrete Beam Calculator: Cubic Yards for Grade Beams & Lintels

Multiply the beam's width by its depth by its length to get cubic feet, then divide by 27 to get cubic yards. This calculator does the conversion automatically once you enter the three dimensions.

A grade beam is a reinforced concrete beam that runs at or below ground level, spanning between piers or footings to support a wall or structure. It spreads loads across the foundation and bridges weak soil.

A grade beam 12 inches wide by 12 inches deep holds 1 cubic foot per linear foot. So a 30-foot run needs about 30 cubic feet, or roughly 1.1 cubic yards.

Grade beams and lintels typically use 3,000 to 4,000 psi concrete, but always follow the structural engineer's specification. The reinforcing steel design, not just the concrete strength, governs the beam's capacity.

Yes, add about 5 to 10% to your calculated volume for over-excavated trenches, form spread, and spillage. Grade beam trenches in particular tend to slump and take more concrete than the nominal size.

For a short lintel you can, using roughly 45 eighty-pound bags per cubic yard as your guide. But for continuous grade beams over about a yard, ready-mix gives more consistent strength and a monolithic pour.

A footing spreads a column or wall load directly onto the soil, while a grade beam spans between supports such as piers or piles and carries the wall load across weak soil. Grade beams are reinforced to act in bending like a beam. Both are estimated as rectangular prisms, but their reinforcement differs greatly.

Reinforcement is set by the structural engineer, but grade beams commonly use longitudinal bars top and bottom with stirrups tying them together. A typical small residential beam might use two or three #4 or #5 bars each face. Never guess rebar for a structural beam; follow the stamped drawings.

On sites with expansive or weak soil, a grade beam supported on drilled piers often replaces a conventional spread footing. The beam bridges between piers so the soil under the beam carries little or no load. This is a structural design decision, not a substitution you make on your own.

Widths are commonly 10 to 16 inches to match the wall above and house the reinforcement cage with adequate cover, but the exact size comes from the engineer. Wider beams obviously increase concrete volume proportionally. Use the actual specified width in the calculator.

Break the beam into uniform prism segments, calculate each segment's volume separately, and add them together. A tapered section can be approximated as the average cross-section times its length. Summing simple prisms keeps the estimate accurate without complex geometry.

Standard concrete weighs about 150 lb per cubic foot, so one cubic yard (27 ft³) weighs roughly 4,050 lb, about two tons. A 30-ft 12×12 grade beam at 30 ft³ therefore weighs near 4,500 lb. That mass matters for handling and for pier design.

Yes. Beams have dense reinforcement, so mechanical vibration is needed to consolidate the mix and remove air pockets around the bars. Poor consolidation leaves voids that weaken the beam. Vibrate in lifts rather than dragging the vibrator horizontally.