Getting a slab order right starts with three measurements and one decision about thickness.
Measure the footprint
Measure the length and width of the slab in feet, or metres. For an irregular shape, split it into rectangles and add the areas.
Choose the thickness
Four inches suits patios and walkways. Driveways and garage floors are usually 5 to 6 inches. Thicker edges and a non level subgrade both add volume, so measure the deepest realistic case.
Turn it into concrete
Volume is length times width times thickness. Convert to cubic yards by dividing cubic feet by 27, then add about 7 percent waste and round up to whole bags. An 80 pound bag yields about 0.60 cubic feet.
Get your exact amount. Concrete Calculator →
Common questions
How much concrete for a 10 by 10 slab at 4 inches?
About 1.24 cubic yards before waste, roughly 56 of the 80 pound bags.
How thick should a slab be?
Four inches for patios and walkways, 5 to 6 inches for driveways and garages.
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.