Concrete for a 12 × 12 slab
Short answer
A 12 × 12 ft slab at 4" thick needs about 1.78 cubic yards of concrete — roughly 89 80-lb or 118 60-lb pre-mix bags (including 10% waste).
Concrete
1.78 yd³
80-lb bags
89
60-lb bags
118
40-lb bags
177
12 × 12 slab at 4" thick
A 12 × 12 ft slab is 144 square feet. At the standard 4-inch thickness that works out to 48 cubic feet, or 1.78 cubic yards including a 10% waste allowance. For a driveway or anything bearing vehicle loads, step up to 5–6 inches.
Different size or thickness?
Open the concrete calculatorOther slab sizes
Frequently asked questions
How much concrete for a 12 × 12 slab?
A 12 × 12 ft slab at 4" thick needs about 1.78 cubic yards (48 cubic feet), including a 10% waste allowance.
How many bags of concrete for a 12 × 12 slab?
About 89 80-lb bags, 118 60-lb bags, or 177 40-lb bags. Above roughly 1 cubic yard it is usually cheaper to order ready-mix than to buy bags.
Is a 4-inch slab thick enough?
Four inches is standard for patios, walkways, and shed floors. Go to 5–6 inches for driveways or anything carrying vehicle loads. Change the thickness in the calculator to see the new amount.