Free Concrete Calculator
Instantly estimate cubic yards, number of bags, and total cost for slabs, footings, columns, and stairs.
Units:
Average ready-mix concrete costs $120-$200 per cubic yard.
Enter dimensions above to see your concrete estimate.
How It Works
1
Select Shape
Choose from rectangular slab, round slab, tube/column, or stairs.
2
Enter Dimensions
Input length, width, and thickness in imperial or metric units.
3
Get Results
See cubic yards, bags needed, truck loads, and estimated cost instantly.
Why Use Our Calculator?
Accurate
Industry-standard formulas for precise concrete volume estimates.
100% Free
No sign-up, no fees, no limits. Use it as many times as you need.
Multiple Shapes
Calculate for slabs, round pads, columns, tubes, and stairs.
Cost Estimation
Enter your local price to get an instant project cost estimate.
Frequently Asked Questions
How do I calculate how much concrete I need?
Measure the length, width, and thickness of your project area. Multiply all three dimensions together to get volume in cubic feet, then divide by 27 to convert to cubic yards. Our calculator handles this automatically for you.
How many bags of concrete do I need for a 10x10 slab?
A 10x10 foot slab at 4 inches thick requires approximately 1.23 cubic yards of concrete. That equals roughly 56 bags of 80-lb concrete mix, 72 bags of 60-lb mix, or 112 bags of 40-lb mix.
What is the standard concrete slab thickness?
The standard thickness for a residential concrete slab is 4 inches. Driveways and garage floors typically require 5-6 inches. For heavy loads or commercial use, 6-8 inches may be needed.
How much does concrete cost per cubic yard?
Ready-mix concrete typically costs between $120 and $200 per cubic yard, depending on your location, mix type, and delivery distance. The national average is around $150 per cubic yard in 2026.
Should I order extra concrete?
Yes, always order 5-10% more concrete than your calculated amount to account for spillage, uneven subgrade, and form variations. Running short mid-pour creates weak cold joints.
What is the difference between 3000 PSI and 4000 PSI concrete?
3000 PSI concrete is the standard mix for sidewalks, patios, and slabs. 4000 PSI is a higher-strength mix used for driveways, garage floors, and structural elements that bear heavier loads.
How many 80-lb bags are in a cubic yard?
One cubic yard of concrete requires approximately 45 bags of 80-lb concrete mix. Each 80-lb bag yields approximately 0.6 cubic feet, or about 0.022 cubic yards of mixed concrete.
When should I use bags vs. ready-mix delivery?
Bags are practical for small projects under 1 cubic yard (fence posts, small pads). For anything over 1-2 cubic yards, ready-mix truck delivery is more cost-effective and produces better results.
Can I use this calculator for footings and foundations?
Yes. Use the rectangular slab shape for spread footings, the tube/column shape for pier footings, or calculate multiple sections separately and add the volumes together.
Does this calculator account for waste?
The calculator gives you the exact volume based on your dimensions. We recommend adding 5-10% to the result for waste, spillage, and subgrade irregularities when placing your order.