Calculate Concrete Yardage
Figure out exactly how many cubic yards of concrete you need. Supports slabs, footings, columns, and irregular shapes.
Concrete Yardage Calculator
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How to Figure Concrete Yardage
Figuring concrete yardage is straightforward once you understand the formula. All ready-mix concrete is ordered and priced by the cubic yard, so converting your project dimensions into cubic yards is the critical first step before calling any concrete plant.
The Basic Formula
For a rectangular slab: (Length × Width × Thickness in feet) ÷ 27 = cubic yards. Since thickness is usually measured in inches, divide it by 12 first to convert to feet. Then add a 10% waste factor.
Worked Example: 20×20 Driveway at 4 Inches
Length × Width: 20 × 20 = 400 square feet. Thickness in feet: 4 ÷ 12 = 0.333. Cubic feet: 400 × 0.333 = 133.3 cubic feet. Cubic yards: 133.3 ÷ 27 = 4.94 yards. With 10% waste: 4.94 × 1.10 = 5.43 yards — so order 5.5 yards.
Rule of thumb: A 4-inch slab requires 1 cubic yard for every 81 square feet. An 8-foot-wide driveway that's 40 feet long (320 sq ft) at 4" needs about 4 cubic yards plus waste.
Common Slab Size Reference
| Slab Size | 4" Thick | 5" Thick | 6" Thick |
|---|---|---|---|
| 10×10 | 1.2 yd³ | 1.5 yd³ | 1.9 yd³ |
| 12×12 | 1.8 yd³ | 2.2 yd³ | 2.7 yd³ |
| 20×20 | 5.0 yd³ | 6.2 yd³ | 7.4 yd³ |
| 24×24 | 7.1 yd³ | 8.9 yd³ | 10.7 yd³ |
| 30×30 | 11.1 yd³ | 13.9 yd³ | 16.7 yd³ |
| 40×60 | 29.6 yd³ | 37.0 yd³ | 44.4 yd³ |
All figures include a 10% waste factor. Actual orders should be rounded up to the nearest 0.5 yard.
How Many Cubic Yards Do You Need? Common Projects
Residential Driveway
A standard single-car driveway (10 ft wide × 20 ft long) at 4 inches requires about 2.5 cubic yards. A double-car driveway (20 ft × 40 ft) at 4 inches requires approximately 10 cubic yards. Most concrete plants will deliver as little as 1 yard but charge a short-load fee for orders under 5-6 yards.
Patio or Backyard Slab
A 12×16 patio at 4 inches needs approximately 2.4 cubic yards. A 20×24 patio needs roughly 6 yards. For patios, 4 inches is the standard residential thickness — no need to go thicker unless you're planning to park on it.
Garage Floor
A 2-car garage (24×24) at 5 inches needs approximately 10.7 cubic yards. At 6 inches, that becomes 12.8 yards. Garage floors are typically poured thicker than patios to support vehicle weight. Always include a vapor barrier beneath garage slabs.
Frequently Asked Questions
- How do you figure concrete yardage?Multiply length (ft) × width (ft) × thickness (convert inches to feet by dividing by 12). Divide by 27 for cubic yards. Multiply by 1.10 for 10% waste. That's your order quantity.
- How many cubic yards for a 10×10 slab?A 10×10 slab at 4" thick = 1.23 cubic yards with waste. At 6" thick = 1.85 cubic yards.
- How many cubic yards are in a concrete truck?A standard ready-mix truck holds 8-10 cubic yards. Most plants will deliver as little as 1 yard but charge a short-load fee for small orders.
- What is the minimum order for ready-mix concrete?Most ready-mix plants have a minimum order of 1 cubic yard but charge a short-load fee for orders under 5-7 yards. The short-load fee typically ranges from $50-$150 depending on the plant and region.
- Should I add extra concrete to my order?Yes, always add 10% extra for residential projects. Running short of concrete mid-pour creates cold joints, which weaken the slab. Most plants allow you to refuse the last yard if you end up not needing it, but you cannot get more concrete delivered quickly once the truck leaves.