How it works
The calculator converts slab depth from inches to feet, finds the rectangular volume, converts cubic feet to cubic yards, and adds the selected waste allowance.
Standard formula
cubic yards = length × width × (depth / 12) / 27 × (1 + waste / 100)Worked example
A 20 ft × 10 ft slab at 4 inches is about 2.47 cubic yards before waste and about 2.72 with 10% waste.
Frequently Asked Questions
Why add waste?
Small losses and uneven ground can require extra concrete. Confirm the allowance with your supplier.
Does this include footings?
No. Add separate shapes or consult a construction professional.
What is the output unit?
The result is cubic yards, a common ordering unit for concrete.
Is the estimate an order quantity?
No. Verify measurements, site conditions, and supplier recommendations.