Concrete Slab Calculator
Use this concrete slab calculator to size any flat pour — patios, shed bases, garage floors, driveways and house slabs. Enter dimensions by feet or meters (or work from square feet with a known thickness) and get volume, bags and cost instantly.
So verwenden Sie diesen Rechner
- Geben Sie Ihre Maße ein — Fuß für Längen, Zoll für die Dicke.
- Optionen anpassen — Verschnitt in Prozent, Sackgröße und Ihr lokaler Betonpreis.
- Ergebnisse ablesen — Volumen, Säcke, Gewicht und Kosten werden live bei der Eingabe aktualisiert.
Die Formel
Slab volume = Length × Width × Thickness; by square feet: Volume (ft³) = Area (ft²) × Thickness (ft) Rechenbeispiel: A 24 × 24 ft garage slab at 4 in: 576 ft² × 0.333 ft = 192 ft³ ÷ 27 ≈ 7.11 yd³ — order 7.5–8 yd³ with waste.
A concrete calculator for slab work needs to get three things right: thickness conversion (inches to feet trips everyone up), waste allowance, and the coverage math when you're working by square feet. This tool handles all three.
Working from area? At 4 inches thick, every 81 square feet needs one cubic yard. At 6 inches, one yard covers just 54 square feet. That's why a concrete slab calculator by square feet always asks for thickness — coverage changes fast.
For fixed-depth pours, jump to the dedicated 2, 3, 6, and 8 inch slab calculators, which lock the thickness so you only enter length and width.
Häufig gestellte Fragen
Häufige Fragen zum concrete slab calculator.
How thick should my concrete slab be?
4 inches for patios, walkways and shed bases; 5–6 inches for driveways; 6–8 inches for garage floors and slabs carrying trucks or equipment (with rebar).
How do I calculate a slab by square feet?
Multiply your area in square feet by the thickness in feet (inches ÷ 12), then divide by 27 for cubic yards. Example: 400 ft² × 0.333 = 133 ft³ ÷ 27 ≈ 4.94 yd³.
How many bags of concrete for a slab?
Divide slab volume in cubic feet by the bag yield: 0.60 ft³ per 80 lb bag, 0.45 ft³ per 60 lb bag. A 10 × 10 ft slab at 4 in needs about 56 × 80 lb bags before waste.
Should I use ready-mix or bags for a slab?
Over about one cubic yard, ready-mix is cheaper and far less labor. Bags suit small pads, repairs and pours where a truck can't reach.
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