Concrete Slab Calculator — ft to cu yd, bags, cost
How to use this calculator
Enter slab dimensions in feet, inches, and fractions (⅛″ precision). Choose from four shapes — rectangle, circle, triangle, or L-shape — set thickness and waste allowance. Results update instantly with volume, area, weight, and an interactive diagram.
Cost — pick ready-mix truck per yd³, 80-lb bags, or 60-lb bags to get the total material cost.
Reinforcement — four welded wire mesh types or four rebar sizes (#3–#6) with spacing 6″–24″ o.c., lap splices per ACI 318-19, and waste allowance.
Labor — rate per ft², per yd³, or a flat price. Grand total sums all active sections.
Saved Calculations
| Time | Shape | Area ft² | Vol yd³ | Concrete $ | Rebar | Qty | Rebar $ | Labor | Total |
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How to Calculate Concrete for a Slab
This concrete slab calculator estimates volume in cubic yards, number of pre-mixed bags (60 lb and 80 lb), total weight, material cost, reinforcement requirements, and labor expenses for rectangular, circular, triangular, L-shaped slabs, or by direct area input in square feet. Enter dimensions in feet, inches, and fractions with ⅛″ precision, set the slab thickness (standard: 4″ for patios, 5–6″ for driveways, 8″ for heavy-duty), and adjust waste allowance from 5% to 20% depending on pour complexity.
Reinforcement per ACI 318-19
Choose welded wire mesh (WWM 6×6 or 4×4 in four gauge options) or rebar #3 through #6 with spacing from 6″ to 24″ on center. The calculator accounts for lap splices at 40 bar diameters, sheet overlap, and cutting waste. Single or double layer placement is supported.
Cost Estimation
Compare ready-mix delivery pricing per cubic yard against bagged concrete (80 lb ≈ 0.6 ft³, 60 lb ≈ 0.45 ft³). Add labor cost per square foot, per cubic yard, or as a flat rate. When multiple cost sections are active, the grand total provides a full project budget breakdown.
Export & Save
Save calculations to the built-in history table and export results as formatted text, CSV spreadsheet, A4 portrait JPG image, or a single-page PDF with diagram and data. All estimates are for planning purposes — consult a licensed structural engineer for load-bearing applications.
