What This Calculator Does
The Concrete Slab Cost Calculator estimates the total price to pour a flat concrete slab — such as a patio, driveway, shed base, or garage floor. It converts your slab dimensions into the volume of concrete required (in cubic yards), multiplies by your local price per cubic yard, and adds labor and finishing costs to give a complete project total.
How to Use It
Enter the slab's length and width in feet and its thickness in inches. Then provide the price you pay per cubic yard of concrete (ready-mix prices commonly range from $120–$170), your labor estimate, and any finishing cost (broom finish, stamping, sealing, etc.). The calculator returns the required concrete volume and a full cost breakdown.
The Formula Explained
First the slab volume is found in cubic feet: length × width × (thickness ÷ 12), since thickness is entered in inches. Because concrete is sold by the cubic yard, that figure is divided by 27 (the number of cubic feet in a cubic yard). The volume in cubic yards is then multiplied by your price per yard, and labor plus finishing are added on top.
$$\text{Total Cost} = \frac{L \times W \times (T/12)}{27} \times \text{Price/yd}^3 + \text{Labor} + \text{Finishing}$$ $$\text{where}\quad \left\{ \begin{aligned} L &= \text{Length (ft)} \\ W &= \text{Width (ft)} \\ T &= \text{Thickness (in)} \end{aligned} \right.$$
Worked Example
For a 20 ft × 20 ft slab that is 4 inches thick: volume = 20 × 20 × (4 ÷ 12) = 133.33 cubic feet = 4.94 cubic yards. At $150 per yard the concrete costs about $740.74. Adding $500 labor and $200 finishing gives a total of roughly $1,440.74.
$$\text{volume} = 20 \times 20 \times (4 \div 12) = 133.33 \text{ cubic feet} = 4.94 \text{ cubic yards}$$FAQ
Should I add extra concrete for waste? Yes — contractors typically order 5–10% extra to cover spillage and uneven subgrade. Increase your thickness or volume slightly to build in a buffer.
Does price per yard include delivery? Ready-mix quotes usually cover delivery within a set radius, but small loads may carry a short-load fee. Confirm with your supplier.
What thickness should I use? 4 inches is standard for patios and walkways; driveways and load-bearing slabs are often 5–6 inches.
