About Concrete Slab, Footing & Bag Calculator
Accurately estimate ready-mix concrete volume and premix bags for slabs, driveways, footings, and cylindrical sonotubes. Features automatic waste factor calculations and weight estimates.
Key Capabilities & Features
- Rectangular slab and circular footing geometry solvers
- Cubic yards, cubic feet, and cubic meters readouts
- Instant conversion to 40lb, 60lb, and 80lb premix bags
- Adjustable waste and spillage buffer (0% to 25%)
- Total estimated weight in pounds and kilograms
How to Use Concrete Slab, Footing & Bag Calculator
Select Shape
Choose between a rectangular slab (patios, driveways) or circular column/footing.
Enter Dimensions
Provide length, width, and depth (thickness) in feet or inches.
Set Waste Factor
Include 10% standard contingency for excavation irregularities and spillage.
View Bag & Ready-Mix Order
Review total cubic yards and the exact number of bags required for your pour.
Privacy & In-Browser Execution Guarantee
100% client-side calculation. Your project measurements never leave your device.
Frequently Asked Questions
How thick should a residential concrete slab be?
Sidewalks and patios typically require 4 inches of concrete, whereas driveways and heavy garage floors should be 5 to 6 inches thick with rebar reinforcement.
How many 80lb bags of concrete are in a cubic yard?
One cubic yard of concrete equals 27 cubic feet. Since one 80lb bag yields approximately 0.60 cubic feet, you need 45 bags (80lb each) per cubic yard.
When is a ready-mix truck cheaper than bagged concrete?
For projects requiring more than 1.5 to 2 cubic yards (~65 to 90 bags of 80lb), ordering a ready-mix concrete truck is typically more economical and guarantees structural consistency.