Formula
Volume uses the selected shape: length × width × depth for rectangles, or π × radius² × depth for circles. Waste is added after net volume.
DIY & HOME PROJECTS
Concrete Calculator
Estimate slabs, round pours or post holes, including waste and bag quantities.
CALCULATOR GUIDE
How to use the Concrete Calculator
Choose a rectangular slab, round pour or post-hole project, then enter dimensions, quantity, waste and bag size.
Worked example
A 10 ft × 12 ft slab at 4 in deep is about 1.48 cubic yards; with 10% extra, plan for about 1.63 cubic yards.
Assumptions and limits
The model assumes uniform dimensions. Irregular forms, uneven subgrades, spillage, reinforcement and supplier minimums can change the order.
Frequently asked questions
How much extra concrete should I order?
A 5–10% allowance is common for a simple pour, but uncertain measurements or complex forms may need more. Confirm with the supplier.
Can I use this for circular slabs or post holes?
Yes. Select the round or post-hole shape and enter the diameter, depth and number of identical pours.
How this calculator works
Enter your known values and select Calculate result. Review units and inputs before relying on the planning estimate.
Actual quantities, prices and requirements can vary. Confirm critical work with a supplier or qualified professional.