Concrete for a 20×24 Slab at 6" Thick

A 20 ft × 24 ft slab poured 6 inches thick is 480 sq ft and needs 8.89 cubic yards of concrete — order 9.60 CY to cover 8% waste, or about 433 80-lb bags for a small pour. Adjust the dimensions below for your project.

Concrete including allowance

9.60 cu yd

Slab area

480 sq ft

Concrete needed

8.89 cubic yards9.60 CY with 8% allowance

80-lb bags

433 bagsor 577 × 60-lb bags

Ready-mix cost (est.)

$1,680$175/CY sample price; delivery and short-load fees extra

How this estimate works

Volume = length × width × (thickness ÷ 12) ÷ 27, in cubic yards. The headline includes your waste allowance (8% by default); do not add it again. Bag counts round up using 0.60 cu ft per 80-lb bag or 0.45 cu ft per 60-lb bag. Confirm the product yield.

The shopping list uses ready-mix plus a sample 4-inch base, mesh, forms, and vapor barrier. These companion materials are starting allowances, not a structural specification. Verify your slab design, reinforcement, strength, and supplier delivery minimums.

Planning estimate. Adjust allowances and sample prices for your supplier; tax, delivery, and labor are not included.

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Concrete for a 20×24 Slab at 6" Thick

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