Concrete Calculator
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What Is a Concrete Calculator?
A concrete calculator estimates how much concrete you need for a slab project, in cubic yards, cubic feet, or pre-mixed bags, based on the length, width, and thickness of your pour area.
Formula Used
Cubic Feet = Length (ft) × Width (ft) × [Thickness (in) ÷ 12]
Cubic Yards = Cubic Feet ÷ 27
Bag counts are estimated using standard yield: roughly 0.6 cubic feet per 80 lb bag, and 0.45 cubic feet per 60 lb bag.
How to Use This Calculator
Enter the length and width of your slab in feet, and the thickness in inches. Click "Calculate Concrete Needed" to see cubic yards, cubic feet, and how many pre-mixed bags you'd need.
Tips for Concrete Projects
Always order 5-10% more concrete than calculated to account for spillage, uneven ground, and forming imperfections. For large pours, ready-mix delivery (ordered by the cubic yard) is usually more economical than bagged concrete.
Frequently Asked Questions
What thickness should I use for a driveway or patio?
Standard patios and walkways are typically 4 inches thick, while driveways often use 4-6 inches depending on vehicle weight and local codes.
Should I order extra concrete?
Yes, most contractors recommend ordering 5-10% extra to account for spillage, form leakage, and ground irregularities.
How much does a bag of concrete cover?
An 80 lb bag yields about 0.6 cubic feet of mixed concrete, and a 60 lb bag yields about 0.45 cubic feet, though this varies slightly by brand.
Is bagged concrete or ready-mix better for large projects?
For large slabs (typically over 1 cubic yard), ready-mix delivery is usually more cost-effective and consistent than mixing many individual bags.