Introduction
The Concrete Slab Calculator helps you figure out how much concrete you need for your project. For a patio, a driveway, or a garage floor, this tool calculates how much concrete you need to order. Just enter the length, width, and thickness of your slab, and the calculator will tell you how many cubic yards or cubic feet of concrete to buy. Ordering the right amount of concrete saves you money and keeps your project on track. Too little concrete means extra trips and delays, while too much means wasted material. Use this calculator before your next pour to get it right the first time.
How to use our Concrete Slab Calculator
Enter the size of your slab below to find out how much concrete you need. The calculator will give you the total volume of concrete in cubic yards and cubic feet.
Length: Type in the length of your concrete slab in feet. Measure from one end to the other along the longest side.
Width: Type in the width of your concrete slab in feet. This is the shorter side measured from edge to edge.
Thickness: Enter the thickness (or depth) of your slab in inches. The International Residential Code sets a minimum of 3½ inches for concrete floors on the ground.1 Sakrete's directions for slabs and walkways call for at least 4 inches of concrete.2
Quantity: If you are pouring more than one slab of the same size, enter the number of slabs here. The calculator will multiply the volume for you so you get a total for all slabs at once.
Concrete Slab Calculator
A concrete slab is a flat, horizontal surface made of poured concrete. It is one of the most common parts of any building project. Slabs are used for floors, driveways, patios, sidewalks, and garage foundations. They are strong, long-lasting, and can support heavy loads when built the right way.
How Concrete Slabs Work
A concrete slab sits on a prepared base of compacted soil or gravel. The typical residential slab is 4 inches thick, but thicker slabs of 5 or 6 inches are used for areas that carry heavier weight, like garages or driveways. The concrete is poured into forms, spread evenly, and then smoothed out before it hardens.
Why Calculating Concrete Matters
Concrete is sold by the cubic yard or cubic meter.3 If you order too little, you'll have to stop your pour and wait for more, which creates a weak joint in the slab. If you order too much, you waste money. A concrete slab calculator helps you figure out exactly how much concrete you need based on the length, width, and thickness of your project.
Tips for a Good Concrete Slab
- Add 4% to 10% extra to your calculated amount to account for spillage, uneven ground, and waste.3
- Use wire mesh or rebar inside the slab. Steel will not stop cracks, but it keeps them from opening up.4
- Compact the base before pouring.5 A loose base leads to settling and cracks over time. Many contractors use a layer of gravel or sand as a sub-base for proper drainage and stability.
- Control joints should be no farther apart than 24 to 36 times the slab thickness, about 10 feet for a 4-inch slab, to guide where cracks form.4
- Cure the concrete by keeping it moist, typically for 3 to 7 days.6 This helps it reach its full strength.
Common Slab Thicknesses
- 4 inches: sidewalks, patios, and shed floors
- 5 inches: residential driveways
- 6 inches or more: garages, heavy equipment pads, and commercial floors
Getting the right amount of concrete before you start your project saves time, money, and headaches. Use the calculator above to quickly find out how many cubic yards of concrete your slab will need.