Concrete Calculator
Estimate the volume of concrete you need for a slab, footing, column or round post hole, in cubic feet, cubic yards and cubic meters.
Result
Enter your numbers to see the estimate.
How this calculator works
Concrete is sold and ordered by the cubic yard in the US (or cubic meter elsewhere), so getting your volume estimate right before you order matters — ready-mix trucks typically have minimum order quantities, and running short mid-pour is a serious problem.
For a rectangular slab or footing, volume is simply length × width × depth. For round shapes like a post hole or column, volume uses the formula for a cylinder: π × radius² × height. This calculator handles both shape types and converts your result into cubic feet, cubic yards and cubic meters so you can compare against your supplier's quote.
Always add a waste allowance — typically 5-10% — to cover uneven ground, spillage and formwork variance. Concrete work involves structural and safety considerations, so for anything load-bearing (foundations, structural slabs, retaining elements), verify your depth, mix strength and reinforcement requirements with a qualified professional or your local building code before pouring.
Example: A 10 ft × 10 ft slab poured 4 in (0.33 ft) deep needs about 33.3 cubic feet, or roughly 1.23 cubic yards, of concrete.
How it works
Enter your measurements or costs
Fill in the room size, materials or costs for your project. No sign-up required.
Adjust the settings
Choose your units, waste percentage and any project-specific options.
Get your estimate instantly
See your results calculated instantly, right in your browser.
Frequently asked questions
How much concrete do I need for a slab?
Multiply the slab's length, width and depth (in feet) to get cubic feet, then divide by 27 to get cubic yards — the unit concrete is typically ordered in. This calculator does that conversion for you.
How do I calculate concrete for a round post hole?
Use the cylinder volume formula: π × radius² × depth. Switch to the round shape option in the calculator and enter the hole's diameter and depth.
How much extra concrete should I order?
Add 5-10% to your calculated volume to cover uneven subgrade, spillage and minor formwork variance, especially on DIY pours.
Is this calculator accurate enough for structural work?
This calculator gives a solid volume estimate, but structural concrete work (foundations, load-bearing slabs) has depth, mix and reinforcement requirements set by local building codes. Always verify structural and safety requirements with a qualified professional.
What's the difference between a footing and a slab?
A footing is typically a narrower strip of concrete that supports a wall or post below grade, while a slab is a flat, poured surface like a patio or driveway. Both use the same rectangular volume formula in this calculator.