Basic
Concrete Slab Calculator
Calculate the exact amount of concrete needed for your slab project. This calculator works for patios, driveways, walkways, garage floors, and any flat concrete surface. Enter your dimensions in feet and get results in cubic yards, cubic feet, and number of concrete bags required.
Enter Your Measurements
Formula Used
Volume (cu ft) = Length × Width × (Depth ÷ 12) Volume (cu yd) = Volume (cu ft) ÷ 27
Pro Tips
- •Always order 10% extra concrete to account for spillage and uneven ground
- •For driveways, use at least 6 inches of depth for vehicle traffic
- •Consider using wire mesh or rebar for reinforcement
- •Temperature affects curing time - avoid pouring in extreme heat or cold
Frequently Asked Questions
How much concrete do I need for a 20x20 slab?
For a 20x20 slab at 4 inches deep, you need approximately 4.94 cubic yards of concrete. Always order about 10% extra, so order 5.5 cubic yards.
How thick should a concrete slab be?
For patios and walkways, 4 inches is standard. Driveways should be at least 6 inches. Garage floors typically use 4-6 inches depending on vehicle weight.
Should I use wire mesh in my concrete slab?
Wire mesh helps control cracking and is recommended for slabs larger than 10x10 feet. For heavy loads, consider using rebar instead.