Check Beam Dimensions Before You Pour
Use this Concrete Beam Size Calculator to work with rectangular beam dimensions, T-beam geometry, target cross-sectional area, beam count, concrete volume and metric beam sizes. The calculator can estimate width, depth, cross-sectional area, cubic feet, cubic yards, concrete bags and optional material cost from dimensions you enter.
Calculate rectangular beams, T-beam geometry, depth from a user-entered target area or metric beam dimensions. Results remain hidden until you press Calculate.
Estimate beam cross section and concrete quantity from width, depth, length and number of beams.
This calculator does not determine whether the entered width and depth are structurally adequate. Use approved structural drawings or engineering for beam sizing.
Estimate T-section concrete area and volume using flange and web dimensions.
This is a geometric T-section model only. Effective flange width, structural capacity, reinforcement and composite action are not calculated.
Convert a user-entered target cross-sectional area into beam depth for a chosen beam width.
The target area must come from a valid project source. This tool only solves Area = Width × Depth and does not determine the area required for structural performance.
Calculate beam cross section and concrete volume using millimeters and meters.
This mode estimates beam geometry and volume only. Structural beam design must be checked separately.
Enter the formed beam width in inches or millimeters.
Use the overall concrete depth shown by the project.
Calculate cubic feet, cubic yards or cubic meters.
Add ready-mix pricing for a basic concrete-material estimate.
A concrete beam is usually described by its width, overall depth and length. The Concrete Beam Size Calculator converts those physical dimensions into cross-sectional area and concrete volume. It can also total several identical beams and calculate an approximate ready-mix order.
Use Rectangular Beam for standard rectangular beams. Use T-Beam Geometry when the concrete section includes a flange and web. Use Target Area only when an approved project source has already provided a required cross-sectional area and you want to solve for a geometric depth at a chosen width. Use Metric Beam for millimeters and meters.
Determine whether the beam is rectangular, T-shaped or another special section.
Use the actual formed dimensions from the project drawings.
Use the physical concrete length for the beam being estimated.
Multiply identical beams into one combined quantity.
Check cubic yards or m³ and add an ordering allowance if appropriate.
For a rectangular beam, cross-sectional area equals beam width multiplied by overall beam depth. Concrete volume then equals that cross-sectional area multiplied by beam length.
Use consistent units before multiplying.
Convert cubic feet to cubic yards by dividing by 27.
A 12-inch-wide by 18-inch-deep beam has a 216-square-inch cross section, which equals 1.5 square feet. Over a 20-foot length, the beam contains 30 cubic feet of concrete, or about 1.11 cubic yards before any ordering allowance.
Width and depth are the two primary geometric dimensions of a rectangular beam. Depth is usually measured vertically through the overall concrete section, while width is measured across the beam. These values strongly influence concrete volume because every extra inch changes the cross-sectional area along the full beam length.
For quantity estimating, use the actual formed dimensions. Do not substitute excavation dimensions, clear span dimensions or reinforcement cage dimensions for the concrete beam size.
A T-beam can be estimated as the area of the flange plus the area of the web below the flange. To avoid double-counting, the web depth used in the second rectangle is the overall beam depth minus flange thickness.
Multiply the final area by beam length and beam count for concrete volume.
This geometric model is useful for concrete quantity only. It does not determine effective flange width, neutral axis, flexural strength, shear strength or reinforcement.
Sometimes an estimator or designer already has an approved target cross-sectional area and wants to see what rectangular depth corresponds to a chosen beam width. The relationship is simple: depth equals area divided by width.
The target area must come from a valid project source; this calculator does not generate it.
For example, a target area of 216 in² with a selected width of 12 inches produces a geometric depth of 18 inches. This does not mean a 12 × 18 beam is structurally adequate for any particular span.
Once beam cross-sectional area is known, concrete quantity is straightforward. Convert the section to square feet, multiply by beam length and by the number of identical beams. Then divide cubic feet by 27 for cubic yards.
For general concrete quantity planning, use the Concrete Calculator. For foundation beams, footings and wall systems, use the Concrete Foundation Calculator.
Very small beams, lintels or repair sections can sometimes be placed using bagged concrete. The rectangular-beam calculator provides an approximate bag count using generic planning yields for 40 lb, 60 lb and 80 lb bags. Always confirm the actual yield printed on the product.
Larger structural beams generally require enough material that ready-mix is the more practical ordering unit. Supplier minimum loads, short-load fees and delivery requirements should be checked before scheduling the pour.
Measure overall beam width, overall concrete depth and beam length from the formed geometry.
Enter a ready-mix price per cubic yard or cubic meter to estimate the concrete-material portion of the beam cost. The calculator multiplies the adjusted beam volume by the entered price.
The cost estimate does not include reinforcing steel, formwork, shoring, pumping, labor, finishing, curing, embedded items, delivery surcharges or engineering.
The rectangular, T-beam and metric calculators provide 0%, 5%, 10% and 15% ordering allowances. Extra material can cover form variation, small losses and ordering increments, but the right allowance depends on project conditions and supplier practice.
Avoid applying the same contingency twice if your beam dimensions or concrete order already include an allowance.
Concrete volume uses the overall physical beam depth. Structural effective depth is a different design quantity.
The physical concrete beam may extend into supports. Use the actual beam length shown for quantity estimating.
The web area below the flange should use overall depth minus flange thickness.
Area alone does not determine whether a beam can safely carry a load.
Convert width and depth before multiplying by a beam length entered in feet.
Multiple identical beams should be multiplied into the total concrete volume.
The calculator uses standard geometry formulas. Its arithmetic is accurate for the beam dimensions entered, but it does not perform reinforced-concrete structural design or verify code compliance.
For technical concrete resources, visit the American Concrete Institute and the National Ready Mixed Concrete Association. For rebar quantity, use the Concrete Rebar Calculator.
You can return to the Concrete Beam Size Calculator above to compare dimensions, beam count and concrete volume.
Common questions about beam width, depth, T-beams, concrete volume, bags and material cost.