Calculate the amount of concrete needed for your construction project
Recommended: 5-10% for simple projects, 10-15% for complex
Enter project dimensions to calculate concrete needed
Concrete is measured and ordered in cubic yards, where one cubic yard equals 27 cubic feet. To calculate the volume needed, multiply your project's length, width, and thickness (all in feet), then divide by 27 to convert to cubic yards. For example, a 10' × 12' slab that's 4 inches thick requires (10 × 12 × 0.333) ÷ 27 = 1.48 cubic yards of concrete.
Slab: Volume = Length × Width × Thickness ÷ 27
Footing: Volume = Length × Width × Depth ÷ 27
Column: Volume = π × (Diameter ÷ 2)² × Height ÷ 27
| Mix Type | Bag Size | Yield per Bag | Bags per Cubic Yard | Best For |
|---|---|---|---|---|
| Pre-Mix | 80 lb | 0.60 cu ft | 45 bags | Small projects, repairs |
| Pre-Mix | 60 lb | 0.45 cu ft | 60 bags | Lighter work, easier handling |
| Pre-Mix | 50 lb | 0.375 cu ft | 72 bags | Very small repairs |
| Ready-Mix | Truck delivery | 1+ cu yd | N/A | Projects over 1 cubic yard |
Always order extra concrete to account for spillage, uneven subgrade, over-excavation, and measurement variations. Running short during a pour can compromise the structural integrity of your project.
| Factor | Ready-Mix Truck | Bagged Concrete |
|---|---|---|
| Best Volume | 1+ cubic yards | Under 1 cubic yard |
| Cost Efficiency | Lower per yard for large projects | More expensive per yard, but no minimum |
| Labor | Less mixing, more placement work | Significant mixing labor required |
| Consistency | Professional mix, uniform quality | Varies by mixing technique |
| Timing | Must pour quickly, crew needed | Work at your own pace |
| Access | Requires truck access to site | Can carry bags anywhere |
Project: Single-car driveway, 20 feet long × 10 feet wide × 4 inches thick
Calculation: 20 × 10 × 0.333 = 66.6 cu ft ÷ 27 = 2.47 cubic yards
With 10% waste: 2.47 × 1.10 = 2.72 cubic yards
Recommendation: Order 3 cubic yards of ready-mix concrete. At $125/yard = $375 total.
Project: Backyard patio, 12 feet × 12 feet × 4 inches thick
Calculation: 12 × 12 × 0.333 = 48 cu ft ÷ 27 = 1.78 cubic yards
With 8% waste: 1.78 × 1.08 = 1.92 cubic yards
Recommendation: Order 2 cubic yards of ready-mix, or use 90 bags of 80lb pre-mix if truck access is limited.
Project: Continuous footing, 40 feet long × 16 inches wide × 8 inches deep
Calculation: 40 × 1.333 × 0.667 = 35.6 cu ft ÷ 27 = 1.32 cubic yards
With 10% waste: 1.32 × 1.10 = 1.45 cubic yards
Recommendation: Order 1.5 cubic yards. Critical structural element, don't run short.
Project: 8 post holes, 12 inches diameter × 36 inches deep each
Calculation: π × (0.5)² × 3 × 8 = 18.85 cu ft ÷ 27 = 0.70 cubic yards
With 15% waste: 0.70 × 1.15 = 0.81 cubic yards
Recommendation: Use 37 bags of 80lb pre-mix. Easier to work with for multiple small pours.
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