Concrete Slab & Driveway Calculator
Please enter valid dimensions.
Estimated Materials Needed
Total Volume (Cubic Yards):
0
Total Volume (Cubic Feet):
0
80lb Premix Bags (Sakrete):
0
60lb Premix Bags:
0
Estimated Cost (Bulk):
$0.00
How to Calculate Concrete for Slabs and Driveways
Whether you are pouring a new patio, a driveway extension, or a foundation for a shed, calculating the correct amount of concrete is crucial. Ordering too little can result in a "cold joint" which weakens the structure, while ordering too much wastes money and creates disposal issues.
This Concrete Slab Calculator uses the standard industry formula to determine volume based on length, width, and thickness, accounting for typical spillage margins.
The Concrete Calculation Formula
To determine how many cubic yards of concrete you need, use the following steps:
- Convert Dimensions: Ensure length and width are in feet, and thickness is converted to feet (divide inches by 12).
- Calculate Cubic Feet: Multiply Length × Width × Thickness (in feet).
- Convert to Cubic Yards: Divide the total cubic feet by 27 (since there are 27 cubic feet in one cubic yard).
- Add Safety Margin: Professionals recommend adding 5-10% for spillage, uneven subgrade, or form bending.
Standard Thickness Guide
- 4 Inches: Standard for residential sidewalks, patios, and garage floors (for light vehicles).
- 5-6 Inches: Recommended for driveways holding heavier vehicles, RV pads, or hot tub bases.
- 8-12 Inches: Typically used for heavy structural foundations or footings.
Premix Bags vs. Truck Delivery
If your project requires less than 1 or 2 cubic yards, using premixed bags (like Sakrete or Quikrete) is often more economical than paying the "short load" fee for a delivery truck. A standard 80lb bag yields approximately 0.60 cubic feet of cured concrete, while a 60lb bag yields about 0.45 cubic feet.