How Much Does a 20x20 Slab of Concrete Cost?

Cost Estimates by Size

The cost of a slab depends on its size, thickness, and whether you do it yourself or hire a contractor. For a 20x20 concrete slab at 4 inches thick, you’ll need about 7.4 cubic yards of concrete. At $125 to $150 per cubic yard, the concrete alone costs between $925 and $1,100. With labor and materials, a professionally poured slab can range from $2,000 to $4,000.

Smaller slabs are cheaper, but the price per square foot is often higher. A 10x10 slab (around 1.25 cubic yards) may cost $250 to $750 depending on labor. A 12x12 slab (about 1.8 cubic yards) usually ranges from $400 to $1,000. Larger projects cost more overall but may have lower costs per square foot. A 24x24 slab can cost $3,000 to $5,000, while a 50x100 slab—often used for barns or shops—can run $30,000 or more.

Thickness and Material Needs

Slab thickness depends on the use. Standard patios or walkways are usually 4 inches thick. Driveways or heavy-load areas may require 5 to 6 inches. A 20x20 driveway slab at 6 inches will use more concrete and cost more than a patio of the same size at 4 inches.

To calculate volume, multiply length × width × thickness (in feet). A 24x24x4 slab equals about 7.1 cubic yards. For DIY work, one cubic yard requires about 45 bags of 80lb concrete. That means hundreds of bags for larger slabs, making equipment like a motor-powered mixer essential for saving time and effort.

For builders needing long-term durability, Baldor electric motor mixers are designed for high-volume use and provide consistent blends, ensuring proper slab thickness and strength every time.

Timing and Conditions

The best time of year to pour a slab is spring or fall, when temperatures are mild. Extreme heat causes concrete to set too quickly, leading to cracks, while freezing conditions can stop curing entirely. Covering and watering the slab during curing helps prevent damage in less-than-ideal conditions.

Bagged mixes like Quikrete are popular for DIY projects. Many people ask if Quikrete is stronger than regular ready-mix. Both can achieve the same strength if properly mixed and cured, but ready-mix delivered from a plant is more consistent for large projects. Quikrete works well for smaller slabs and repair work.

DIY vs. Professional Pouring

Pouring your own slab can save money, but it requires planning, tools, and labor. For a 20x20 slab, you’ll need equipment like wheelbarrows, screeds, and a concrete mixer. Hiring professionals may cost more, but they bring experience, labor, and finishing skills that ensure a smooth, durable surface.

On average, a DIY 20x20 slab may cost under $1,500 if you handle the work yourself. A contractor may charge double or triple, depending on prep work, reinforcement, and finishing. For high-traffic areas like driveways or shop floors, many homeowners choose professionals to guarantee long-term performance.

Adding moisture control under the slab is also important. Products like a concrete vapor barrier wrappings to protect against ground moisture, extending the life of your concrete and reducing cracking over time.