What this estimate includes
This estimate shows concrete volume, cubic feet, cubic yards, and common bag counts for your slab dimensions.
Before you order
Slab thickness, base prep, uneven ground, reinforcement, and waste can change the final quantity. Use this as a planning estimate and confirm with your concrete supplier before ordering.
Need other outdoor estimates? Try the gravel calculator or paver calculator.
Frequently Asked Questions
How much concrete do I need for a 10x10 slab?
At 4 inches thick, a 10x10 slab needs about 1.23 cubic yards or roughly 56 bags of 80 lb concrete. At 6 inches thick, that rises to about 1.85 cubic yards or 84 bags. Always add 10% for waste.
How many 80 lb bags make one cubic yard of concrete?
An 80 lb bag yields about 0.60 cubic feet. One cubic yard equals 27 cubic feet, so you need approximately 45 bags of 80 lb concrete per cubic yard.
How thick should a concrete slab be?
For a standard patio or walkway, 4 inches is typical. For a garage floor or driveway, 5-6 inches is recommended. For heavy vehicle traffic, 6 inches or more with rebar. Check local building codes for any permitted structure.
When should I use ready-mix instead of bags?
If your job is over 1 cubic yard (about 45 bags of 80 lb), a ready-mix truck is faster, cheaper per unit, and more consistent. Under 1 yard, bags are fine for most DIYers. The break-even depends on local pricing and short-load fees.
How much extra concrete should I order?
Add 10% for DIY bag work. Add 5-8% for ready-mix and round up to the nearest half yard. For uneven or rocky ground, add 10-15%. Running short mid-pour is one of the most expensive mistakes on a slab job.
Do I need rebar in a concrete slab?
For patios and shed bases, rebar is optional but recommended for slabs over 10 feet in any direction. For driveways and garage floors bearing vehicle weight, rebar or wire mesh is standard. Check local code before any permitted pour.
What is the difference between concrete and cement?
Cement is the binding powder ingredient in concrete. Concrete is the finished mix of cement, sand, aggregate, and water. A "bag of concrete" contains all dry ingredients pre-blended -- you just add water.
Can I pour concrete in cold weather?
Do not pour when temperatures are at or below 40 degrees F without cold-weather precautions. Freezing before curing permanently damages the slab. Keep temps above 50 degrees F for at least 7 days after the pour.