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How Much Concrete for a 12 × 12 Slab?

A 12 × 12 ft slab is 144 sq ft. It needs 1.96 cubic yards of concrete at 4 inches thick or 2.93 yd³ at 6 inches, including 10% extra.

12 × 12 ft slab, 10% extra included
Order4 in thick6 in thick
Cubic yards1.962.93
80-lb bags88132
60-lb bags118176
50-lb bags141212
40-lb bags176264
Cubic meters1.502.24
What are you pouring?
Units

Slab, patio or driveway

4 in is typical for patios and walks; 5–6 in for driveways and garage floors.

Bag size
Add your prices (optional)

Use your supplier's prices. We don't show average prices because they vary too much by area.

Concrete needed

1.96 cubic yards

52.8 ft³ · 1.50 m³ · includes 10% extra

You need about 1.96 cubic yards of concrete, or 88 bags of 80 lb mix.

Bags of premix

  • 17640 lb bags
  • 14150 lb bags
  • 11860 lb bags
  • 8880 lb bags
  • Before extra1.78 yd³ (48.0 ft³)
  • Weight of bags7,040 lb
  • Ready-mix costAdd a price per yd³
  • Bagged costAdd a price per bag

One 80 lb bag makes about 0.60 ft³ (manufacturer's published yield). Bags are rounded up.

At 1.96 yd³ that is 88 × 80 lb bags (7,040 lb) to mix. Most people order ready-mix at this size; ask suppliers for their minimum load and any short-load fee.

Estimate only, not a quote or engineering advice. Disclaimer

A 12 × 12 ft slab is a popular patio and shed size, and a common pad for larger hot tubs and gazebos.

12 × 12 slab at other thicknesses

Concrete for a 12 × 12 ft slab
Thicknessyd³ exactyd³ +10%80-lb bags60-lb bags
3.5 in1.561.7177103
4 in1.781.9688118
5 in2.222.44110147
6 in2.672.93132176
8 in3.563.91176235

How it's worked out

12 × 12 = 144 sq ft · 144 × 4 ÷ 12 = 48.0 ft³ · ÷ 27 = 1.78 yd³ · × 1.10 = 1.96 yd³

For bags, the 52.8 ft³ (with extra) is divided by each bag's yield: 0.60 ft³ for 80 lb, 0.45 for 60 lb, 0.375 for 50 lb and 0.30 for 40 lb, then rounded up. At 4 inches the slab itself weighs about 6,700 lb, using the 140 lb/ft³ unit weight QUIKRETE lists for its Concrete Mix.

Bags or a truck?

At 1.96 yd³ you would need 88 × 80-lb bags (about 7,040 lb) and a long session with a mixer and helpers. Most people order ready-mix at this size: call suppliers with the yardage and ask for their minimum load and any short-load fee.

Don't forget the base: most slabs sit on a compacted layer of gravel, and thicker edges or footings around the perimeter add concrete. Use the footing calculator for a thickened edge.

Frequently asked questions

How many yards of concrete for a 12x12 slab?

1.78 cubic yards at 4 inches thick and 2.67 yd³ at 6 inches, before waste. With 10% extra, order 1.96 or 2.93 yd³.

How many bags of concrete for a 12x12 slab?

At 4 inches with 10% extra: 88 bags of 80-lb mix, 118 of 60 lb, 141 of 50 lb or 176 of 40 lb. At 6 inches: 132 bags of 80 lb or 176 of 60 lb.

How many cubic feet of concrete for a 12x12 slab?

48.0 ft³ at 4 inches (144 sq ft × 4 ÷ 12) and 72.0 ft³ at 6 inches, before waste.

How thick should a 12x12 slab be?

Four inches is usual for patios, walkways and shed pads. Garage floors, driveways and pads for heavy loads are commonly 5 to 6 inches. Follow local code or your plans for anything structural.

Other slab sizes

Related

Sources