Thickness is the single biggest driver of how much concrete a slab needs, and it depends on the load.
Typical thicknesses
- Patios and walkways: 4 inches, about 10 cm.
- Driveways for cars: 4 to 5 inches.
- Garage floors and heavier vehicles: 5 to 6 inches, about 13 to 15 cm.
Reinforcement and base
Many slabs use wire mesh or rebar and a compacted gravel base. These do not change the concrete volume much, but they matter for strength. For structural or code regulated work, follow local requirements and a professional's specification.
Effect on volume
Going from 4 to 6 inches increases the concrete by half. Always measure the real thickness, including any thickened edges.
Try different thicknesses. Concrete Calculator →
Common questions
How thick should a driveway slab be?
Four to five inches for cars, 5 to 6 inches for heavier vehicles.
Does thickness change how much concrete I need?
Yes, directly. A 6 inch slab needs 50 percent more concrete than a 4 inch slab of the same area.
More Calculators
Concrete New
Enter slab dimensions. Result rounds up with a 7 percent waste allowance.
Gravel New
Enter the area dimensions and depth. Result rounds up with a 5 percent waste allowance.
Mulch New
Enter the bed area and depth. Result rounds up with a 5 percent allowance.
Topsoil New
Enter the area and depth. Result rounds up with a 5 percent allowance.
Paint New
Enter total wall area and coats. Result rounds up to whole units.
Flooring New
Enter room area and the coverage printed on the box. 10 percent waste added.
Tile New
Enter the area and one tile size. 10 percent waste added.
Drywall New
Enter total area to cover. 10 percent waste added.
Paver New
Enter the patio size and one paver size. 5 percent waste added.
Sand New
Enter the area and depth. 5 percent allowance added.
Roofing New
Enter the roof surface area. 10 percent waste added. Three bundles per square.
Insulation New
Enter area to cover and the coverage printed on the package. 5 percent added.
Fence New
Enter total fence length and post spacing.
Sod New
Enter the area to cover. 5 percent allowance added.
Grass Seed New
Enter area and seeding rate. Default rates suit a new lawn.
Fertilizer New
Enter area, target nitrogen rate and the first number on the bag.
Cubic Yards New
Enter length, width and depth. No waste added.
Square Footage New
Enter length and width.
Board Foot New
Enter board dimensions and quantity.
Material Cost New
Enter quantity, unit price, tax and delivery. Figures are in your own currency.