Concrete Calculator

Calculate cubic yards of concrete needed for slabs, columns, and footings. See bags needed and estimated cost.
Shape
ft
ft
in

Cubic Yards

2.72

80lb Bags

123

Estimated Cost

$407.41

Concrete Calculation Breakdown

Volume (before waste)66.67 cu ft
Waste Factor (10%)+ 6.67 cu ft
Total Volume73.33 cu ft
Cubic Yards Needed2.72
80lb Bags Needed123
Estimated Cost ($150/yard)$407.41
Total Weight5.50 tons (11,000 lbs)

Use the Concrete Calculator above to calculate your results. Enter your values and see instant results — all calculations run in your browser.

Disclaimer: This calculator is for informational purposes only and does not constitute tax, financial, or legal advice. Results are estimates based on the information you provide and current rates. Always consult a qualified tax professional or financial advisor for advice specific to your situation.

How It Works

Our Concrete Calculator precisely determines the cubic yards of concrete required for your 2026 construction projects, whether it's a new patio slab, structural columns, or foundation footings. This tool is crucial for accurate material ordering, preventing costly overruns or construction delays, especially with the projected 4.5% increase in concrete prices by mid-2026.

The calculation methodology employs standard volumetric formulas: for slabs, it's Length x Width x Thickness (converted to feet and cubic yards); for columns, it's Pi x (Radius)^2 x Height; and for footings, it's Length x Width x Depth. These volumes are then rounded up to the nearest quarter cubic yard to account for waste and spillage, a common industry practice.

Always add a 5-10% waste factor for concrete, especially for complex forms or uneven subgrades. A common mistake is underestimating the thickness of a slab or the diameter of a column, leading to shortages. Ensure your measurements are consistent (all in feet or all in inches before conversion) to avoid significant errors.

Example: Driveway Slab with Bagged Concrete Cost

  1. 1 You're pouring a new driveway slab: 40 feet long, 12 feet wide, and 6 inches thick. The local concrete bag mix requires 0.025 cubic yards per 80lb bag, and the average cost per bag in early 2026 is $5.80.
  2. 2 First, convert thickness to feet: 6 inches = 0.5 feet. Volume = 40 ft * 12 ft * 0.5 ft = 240 cubic feet. Convert to cubic yards: 240 cubic feet / 27 cubic feet/yard = 8.89 cubic yards. Adding a 7% waste factor: 8.89 * 1.07 = 9.51 cubic yards.
  3. 3 Rounding up to the nearest quarter yard for ordering: 9.75 cubic yards. Number of bags needed: 9.75 cubic yards / 0.025 cubic yards/bag = 390 bags.
  4. 4 The estimated total cost for bagged concrete for your driveway is 390 bags * $5.80/bag = $2,262. This excludes delivery and labor, providing a clear material budget.

Source: HomeAdvisor · Last updated: April 2026

Frequently Asked Questions

How many bags of concrete do I need?
An 80-lb bag of premix concrete covers about 0.6 cubic feet. For a 10x10 foot slab that is 4 inches thick, you need about 1.23 cubic yards or approximately 56 bags of 80-lb premix.
How do I calculate cubic yards of concrete?
Multiply length x width x depth in feet, then divide by 27 (cubic feet per cubic yard). For a 20x10 foot slab at 4 inches (0.33 feet) thick: 20 x 10 x 0.33 / 27 = 2.44 cubic yards.
How much does a concrete slab cost?
Ready-mix concrete costs $125-160 per cubic yard delivered. For a typical 20x20 foot slab (4 inches thick), material costs run $600-1,000. With professional labor, total costs are $2,400-4,800 depending on your area.

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