How to Calculate Concrete Volume
Whether you are pouring a concrete patio, driveway, or post hole footings, ordering the right amount of concrete is critical. Running short in the middle of a pour creates weak joints, while over-ordering wastes money. Our Concrete Slab Calculator does the exact math to provide you with the volume in cubic yards, cubic meters, and premixed bags.
If you are preparing a site and need to dig out the area first, you might also find our Excavation Calculator useful.
The Mathematical Formula
Concrete is ordered and priced by volume, typically measured in Cubic Yards in the United States and Cubic Meters internationally.
To find the volume manually:
- Measure your Length, Width, and Depth.
- Convert all measurements to Feet. (e.g., a 4-inch depth is 4/12 or 0.33 feet).
- Multiply Length × Width × Depth to get Cubic Feet.
- Divide the Cubic Feet by 27 to get your final Cubic Yards.
Premixed Bags vs. Ready-Mix Truck
How much does a bag of concrete yield? Here are the standard averages:
- 80 lb bag: Yields ~0.60 cubic feet (requires 45 bags per yard)
- 60 lb bag: Yields ~0.45 cubic feet (requires 60 bags per yard)
- 40 lb bag: Yields ~0.30 cubic feet (requires 90 bags per yard)