Concrete Calculator
Estimate the amount of concrete needed for a slab.
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Plan Your Construction Project
Planning a DIY or construction project involving concrete? Our Concrete Calculator helps you estimate the volume of concrete you'll need for a rectangular slab. Enter the dimensions to find the required volume in cubic yards, and get a handy estimate for how many pre-mix bags you might need.
The Formula Explained
- Calculate Volume in Cubic Feet:
Volume = Length (ft) * Width (ft) * Depth (ft)(Note: Depth is often measured in inches, so it must be converted to feet by dividing by 12.) - Convert to Cubic Yards:
Cubic Yards = Volume in Cubic Feet / 27(Since 1 cubic yard = 3 ft × 3 ft × 3 ft = 27 cubic feet)
How to Use the Calculator
- Enter Dimensions: Input the Length and Width of your slab. Choose your units (feet, inches, or meters).
- Enter Depth: Input the thickness of the slab in inches.
- Calculate: The tool will provide the total volume needed in cubic yards and an estimate of how many 60lb or 80lb bags this equates to.
Real-World Example
You want to pour a patio slab that is 10 feet long, 12 feet wide, and 4 inches thick.
- Length: 10 ft
- Width: 12 ft
- Depth: 4 in = 4/12 ft ≈ 0.333 ft
- Volume (cubic feet):
10 * 12 * 0.333 = 40 cubic feet - Volume (cubic yards):
40 / 27 ≈ 1.48 cubic yards
Frequently Asked Questions (FAQ)
- How many bags of concrete do I need? The yield of concrete bags varies. A standard 80-lb bag yields about 0.60 cubic feet, and a 60-lb bag yields about 0.45 cubic feet. The calculator provides an estimate based on these values.
- Should I order extra concrete? Yes, it's a common practice to order about 5-10% extra concrete to account for uneven ground, spillage, and variations in slab depth.
- What about circular slabs or other shapes? This calculator is for rectangular slabs. For other shapes, you would first need to calculate the area of the shape and then multiply by the depth to find the volume.