How much concrete do I need?

What Is Concrete and How Does It Work?

Concrete is a composite material made from three primary ingredients: Portland cement, aggregate (sand and gravel), and water. When mixed together, a chemical reaction called hydration binds the ingredients into a rock-hard mass that can support enormous loads. Unlike cement — which is just one ingredient — concrete is the finished building material you actually pour and shape.

The ratio of these ingredients determines the concrete’s strength, measured in PSI (pounds per square inch). Standard residential concrete is typically 3,000–4,000 PSI, which is strong enough for driveways, patios, sidewalks, and foundation footings. Higher-strength mixes of 5,000+ PSI are used for commercial and structural applications.

Bags vs. Ready-Mix Truck: Which Should You Use?

The decision between bagged concrete and a ready-mix truck delivery comes down to volume. As a general rule:

• Under 2 cubic yards: Use bags. For small projects like setting fence posts, pouring a small pad, or repairing a section of sidewalk, bagged concrete mix is practical and cost-effective. You can mix it in a wheelbarrow or portable mixer at your own pace.
• Over 2 cubic yards: Order a ready-mix truck. Mixing more than 2 cubic yards by hand is exhausting and time-consuming — and you risk inconsistent mixes between batches. A ready-mix truck delivers uniform, professionally batched concrete and can pour the entire project in minutes.

For projects right around the 2-yard mark, consider the complexity of the pour. If you need to finish a large, flat slab quickly before it sets, a truck gives you better results even at smaller volumes.

Recommended Slab Thickness

Choosing the right thickness is critical for durability. Pour it too thin and the slab will crack under load; too thick and you waste money on extra concrete. Here are the standard recommendations:

• 4 inches: Patios, walkways, sidewalks, and shed floors. This is the minimum thickness for any slab on grade and is suitable for foot traffic and light furniture.
• 6 inches: Driveways, garage floors, and any surface that supports vehicles. The extra 2 inches significantly increases load-bearing capacity. Most building codes require 6 inches for driveways.
• 8+ inches: Heavy equipment pads, commercial loading docks, and structural footings. These applications often require engineering specifications and reinforcement with rebar.

Regardless of thickness, always pour your slab on a compacted gravel base (typically 4 inches of crushed stone) to improve drainage and prevent settling.

Always Order 10% Extra

No concrete pour goes perfectly. You will lose material to spillage, uneven subgrade, forms that bulge slightly, and the concrete that sticks to your tools and wheelbarrow. The industry-standard recommendation is to order 10% more than your calculated amount.

For example, if your calculation shows you need 4.94 cubic yards for a 20×20 patio, order 5.5 cubic yards. Running short mid-pour is far worse than having a little extra — cold joints (where fresh concrete meets partially-cured concrete) are a structural weak point and look terrible.

Concrete Curing Tips

Pouring the concrete is only half the job. Proper curing is what gives concrete its full strength. Here is what you need to know:

• Keep it moist: Concrete needs water to cure. Cover fresh concrete with plastic sheeting or apply a curing compound to prevent moisture loss. In hot, dry weather, mist the surface with water several times a day for the first week.
• Temperature matters: Ideal curing temperature is 50–75°F (10–24°C). Below 50°F, curing slows dramatically. Below freezing, uncured concrete can be permanently damaged. In cold weather, use insulating blankets.
• Timing: Concrete reaches about 70% of its rated strength in 7 days and full strength at 28 days. You can walk on it after 24–48 hours, drive on it after 7 days, and place heavy loads after 28 days.
• Do not overwork the surface: Excessive troweling brings too much water and fine cement to the surface, creating a weak top layer prone to flaking (spalling).

Cost Estimates for Concrete in 2026

Concrete costs vary by region, but here are typical 2026 price ranges to help you budget:

• Ready-mix delivery: $140–$160 per cubic yard, with most companies requiring a minimum order of 1 yard. Short-load fees apply for orders under the truck’s capacity (typically 8–10 yards).
• Bagged concrete (80lb): $5–$8 per bag at home improvement stores. Each 80lb bag yields approximately 0.6 cubic feet. For a full cubic yard, you need about 45 bags — making bags significantly more expensive per yard than ready-mix at larger volumes.
• Labor (if hiring): $8–$18 per square foot for a finished, poured slab including forms, gravel base, and finishing.

Do not forget to budget for related materials: gravel base ($20–$30 per ton), rebar or wire mesh ($0.50–$1.50 per square foot), form lumber, and expansion joint material.

Common Concrete Projects and What They Require

To help you plan, here is a quick reference for popular residential projects:

• 10×10 patio (4″ thick): 1.23 cubic yards — a manageable weekend project with bags or a small ready-mix order.
• Two-car driveway (20×20, 6″ thick): About 7.4 cubic yards — definitely a ready-mix truck job.
• Sidewalk (3×30, 4″ thick): 1.11 cubic yards — borderline between bags and a truck delivery.
• Fence post holes (8 holes, 12″ dia × 36″): About 0.7 cubic yards total — easily handled with bags mixed on site.