Concrete Cubic Yard Calculator
Estimate concrete volume in cubic yards and cubic feet from length, width, and thickness. Add a waste factor and an optional bag count for small placements.
Enter your values, then press Calculate.
How to calculate
Enter the length and width of the placement and the thickness of the slab, footing, or wall. Thickness is usually measured in inches in the field. Choose a waste factor for over-excavation, over-pour, and pump residue. The calculator converts everything to feet, multiplies for cubic feet, then divides by 27 for cubic yards.
Formula
Volume (ft³) = length (ft) × width (ft) × thickness (ft). Cubic yards = ft³ ÷ 27. Waste multiplies the neat volume. Bag counts use typical yields of 0.30 ft³ (40 lb), 0.45 ft³ (60 lb), and 0.60 ft³ (80 lb).
Common use cases
- Residential and commercial slab pours
- Footings, sidewalks, and pads
- Quick field checks before calling the ready-mix plant
- Bagged concrete estimates for small patches
Worked example
Example: 10x10 slab at 4 inches with 10% waste
1. Convert thickness to feet
4 in ÷ 12 = 0.3333 ft
2. Neat volume in cubic feet
10 ft × 10 ft × 0.3333 ft = 33.3333 ft³
3. Convert to cubic yards
33.3333 ft³ ÷ 27 = 1.2346 yd³
4. Apply waste factor
1.2346 × (1 + 10%) = 1.358 yd³
5. Bag count from typical yield
ceil(36.6667 ft³ ÷ 0.6 ft³/80 lb bag) = 62 bags
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FAQ
How many cubic yards of concrete do I need?
Multiply length × width × thickness in feet, then divide by 27. A 10 ft × 10 ft × 4 in slab is 1.235 cubic yards before waste.
Why divide by 27?
One cubic yard is 27 cubic feet (3 ft × 3 ft × 3 ft). Ready-mix is ordered in cubic yards in the U.S.
How much waste should I add?
5–10% is common for slabs on grade. Use more for irregular subgrade, thick footings, or pumped placements. Confirm with the supplier.
Are bag counts exact?
No. Bag yields vary by brand and mix. The values here are typical published yields for estimating only.
Disclaimer
These calculators are estimating tools for planning and field checks. They are not a substitute for approved plans, specifications, licensed professional engineering, or governing standards. Confirm densities, waste factors, and yields with your supplier and project documents.