**How many Bags of Concrete do I need for a Slab?**

One of the main questions before laying concrete is how many bags of concrete do I need for a Slab or any concrete component? Right estimation is important, to avoid excess and deficiency.

To determine the number of bags of concrete, you should know the dimensions of the concrete slab (i.e. Length, width and thickness. Once you know the measurements you can calculate the volume of the concrete slab. Premix Concrete bags generally available in the USA are 40lb, 60lb, 80lb and 90lb. A 40lb yields about 0.30 cubic feet.

A 60 lb cement bag yields about 0.45 cubic feet. An 80 lb concrete bag cover about 0.60 cubic feet. A 90 lb concrete bag covers about 0.68 cubic feet.

Dividing the volume with yield will give you the number of bags required for that slab.

Concrete Bag | Yield in cubic feet | Yield in a cubic yard (divided by 27) |

20 lb | 0.15 cubic feet | 0.005 |

40 lb | 0.30 cubic feet | 0.011 |

60 lb | 0.45 cubic feet | 0.017 |

80 lb | 0.60 cubic feet | 0.022 |

90 lb | 0.68 cubic feet | 0.025 |

**How many bags of concrete do I need for a 2×2 Slab**

- Let us assume the thickness of the slab is 4 inches.
- The square footage of the slab will be 2×2 = 4 square feet.
- Now calculate the volume of the slab, Square footage x (thickness in feet).

=4x(4/12)= 4 x 0.3333= 1.332 cubic feet.

- Let us assume we are using a 40 lb concrete bag. 1 bag of 40 lb yields 0.30 cubic feet.
- No. of bags for 2×2 slab 4 inches thick = 1.332/0.30= 4.44
- We can also add 10% extra for wastage. 4.44 + 4.44×10%= 4.88 bags. Thus you will need 5 bags of 40lb weight for a 2×2 slab, 4 inches thick.

**How many bags of concrete do I need for a 2×4 Slab**

- Let us assume the thickness of the slab is 6 inches. Convert it to feet. 6 inch = 6/12= 0.5 foot.
- Calculate the Square footage of the slab i.e. 2 x 4 = 8 square feet.
- Calculate the volume of the slab = 8 x 0.5 = 4.0 cubic feet.
- Let us assume we are using a 60 lb bag, the yield of 1 60 lb bag = 0.45 cubic feet.
- No. of bags for 2×4 slab 6 inches thick = 4.0/0.45 =8.88
- Add 10% extra for wastage, = 8.88×10%+8.88=9.77. Thus for a 2 x 4 slab, 6-inch thick 10 bags of 60lb weight will be required.

**How many bags of concrete do I need for a 4×4 slab**

- Assume a thickness of 4 inches.
- The square footage of the slab will be 4×4 = 16 square feet.
- The volume of the slab = 16 x 0.3333 = 5.33 cubic feet.
- Suppose we are using an 80 lb bag, the yield of 80 lb bag = 0.60 cubic feet.
- No. of bags of concrete for 4×4 slab 4 inches thick = 5.33/0.60 = 8.88
- Add 10% extra for wastage, = 8.88×10%+8.88=9.77= 10 bags

**How many bags of concrete do I need for a 4×6 slab**

- Let the thickness of the slab be 6 inches.
- Area of slab = 4×6= 24 square feet.
- Volume of the slab = 24x(6/12) = 12 cubic feet.
- For a 60 lb concrete bag, the number of bags = 12/0.45= 26,67 bags
- Add 10% extra for wastage, = 26.67×10%=26.67= 29.34= say 29 bags.

**How many bags of concrete do I need for a 4×8 slab**

- Let the thickness of the slab be 4 inches.
- Area of slab = 4×8= 32 square feet.
- Volume of the slab = 32x(4/12) = 10.67 cubic feet.
- For a 40 lb concrete bag, the number of bags = 10.67/0.30= 35.57 bags
- Add 10% extra for wastage, = 35.57×10%+35.57= 39.13= say 39 bags.

How many bags of Concrete do I need for a Slab?

We have made a table wherein the first column size of the slab is mentioned. Square footage for that size of slab is calculated in 2nd column. No. of 40lb, 60lb, and 80 lb bags are calculated for a 4-inch thick slab and a 6-inch thick slab.

How many bags of concrete do I need for a | Square footage | Vol. of the 4-inch thick Slab | Vol of the 6 inch thick slab | No. of bags of 40 lb Concrete | No. of bags of 40 lb Concrete | No. of bags of 60 lb Concrete | No. of bags of 60 lb Concrete | No. of bags of 80 lb Concrete | No. of bags of 80 lb Concrete |

4 inch thick slab | 6 inch thick slab | 4 inch thick slab | 6 inch thick slab | 4 inch thick slab | 6 inch thick slab | ||||

2×2 Slab | 4 | 1.33 | 2.00 | 5 | 7 | 3 | 5 | 2 | 4 |

2×4 slab | 8 | 2.67 | 4.00 | 10 | 15 | 7 | 10 | 5 | 7 |

3×3 Slab | 9 | 3.00 | 4.50 | 11 | 17 | 7 | 11 | 6 | 8 |

4×3 Slab | 12 | 4.00 | 6.00 | 15 | 22 | 10 | 15 | 7 | 11 |

4×4 slab | 16 | 5.33 | 8.00 | 20 | 29 | 13 | 20 | 10 | 15 |

4×5 Slab | 20 | 6.67 | 10.00 | 24 | 37 | 16 | 24 | 12 | 18 |

4×6 slab | 24 | 8.00 | 12.00 | 29 | 44 | 20 | 29 | 15 | 22 |

4×8 slab | 32 | 10.67 | 16.00 | 39 | 59 | 26 | 39 | 20 | 29 |

4×12 Slab | 48 | 16.00 | 24.00 | 59 | 88 | 39 | 59 | 29 | 44 |

5×5 Slab | 25 | 8.33 | 12.50 | 31 | 46 | 20 | 31 | 15 | 23 |

5×10 Slab | 50 | 16.67 | 25.00 | 61 | 92 | 41 | 61 | 31 | 46 |

6×4 Slab | 24 | 8.00 | 12.00 | 29 | 44 | 20 | 29 | 15 | 22 |

6×6 Slab | 36 | 12.00 | 18.00 | 44 | 66 | 29 | 44 | 22 | 33 |

7×7 Slab | 49 | 16.33 | 24.50 | 60 | 90 | 40 | 60 | 30 | 45 |

8×8 slab | 64 | 21.33 | 32.00 | 78 | 117 | 52 | 78 | 39 | 59 |

8×10 Slab | 80 | 26.67 | 40.00 | 98 | 147 | 65 | 98 | 49 | 73 |

9×9 Slab | 81 | 27.00 | 40.50 | 99 | 149 | 66 | 99 | 50 | 74 |

10×8 Slab | 80 | 26.67 | 40.00 | 98 | 147 | 65 | 98 | 49 | 73 |

10×10 slab | 100 | 33.33 | 50.00 | 122 | 183 | 81 | 122 | 61 | 92 |

10×12 slab | 120 | 40.00 | 60.00 | 147 | 220 | 98 | 147 | 73 | 110 |

10×15 Slab | 150 | 50.00 | 75.00 | 183 | 275 | 122 | 183 | 92 | 138 |

10×20 slab | 200 | 66.67 | 100.00 | 244 | 367 | 163 | 244 | 122 | 183 |

12×8 Slab | 96 | 32.00 | 48.00 | 117 | 176 | 78 | 117 | 59 | 88 |

12×10 Slab | 120 | 40.00 | 60.00 | 147 | 220 | 98 | 147 | 73 | 110 |

12×12 slab | 144 | 48.00 | 72.00 | 176 | 264 | 117 | 176 | 88 | 132 |

12×16 Slab | 192 | 64.00 | 96.00 | 235 | 352 | 156 | 235 | 117 | 176 |

12×20 Slab | 240 | 80.00 | 120.00 | 293 | 440 | 196 | 293 | 147 | 220 |

12×24 slab | 288 | 96.00 | 144.00 | 352 | 528 | 235 | 352 | 176 | 264 |

15×15 Slab | 225 | 75.00 | 112.50 | 275 | 413 | 183 | 275 | 138 | 206 |

16×16 slab | 256 | 85.33 | 128.00 | 313 | 469 | 209 | 313 | 156 | 235 |

20×20 Slab | 400 | 133.33 | 200.00 | 489 | 733 | 326 | 489 | 244 | 367 |

## FAQs

### How many bags of concrete do I need for a 2×2 Slab

The square footage for the 2×2 slab is 4.

No. of bags of Concrete for a 4-inch thick slab

40 lb bags: 5

60 lb bags: 3

80 lb bags: 2

No. of bags of Concrete for 6 inch-thick slab

40lb bags: 7

60 lb bags: 5

80 lbs bags: 4

### How many bags of concrete do I need for a 2×4 Slab

The square footage for the 2×4 slab is 8.

No. of bags of Concrete for a 4-inch thick slab

40 lb bags: 10

60 lb bags: 7

80 lb bags: 5

No. of bags of Concrete for 6 inch-thick slab

40lb bags: 15

60 lb bags: 10

80 lbs bags: 7

**How many bags of concrete do I need for a 3×3 Slab**

The square footage for the 3×3 slab is 9.

No. of bags of Concrete for a 4-inch thick slab

40 lb bags: 11

60 lb bags: 7

80 lb bags: 6

No. of bags of Concrete for 6 inch-thick slab

40lb bags: 17

60 lb bags: 17

80 lbs bags: 8

**How many bags of concrete do I need for a 4×3 Slab**

The square footage for the 4×3 slab is 12.

No. of bags of Concrete for a 4-inch thick slab

40 lb bags: 15

60 lb bags: 10

80 lb bags: 7

No. of bags of Concrete for 6 inch-thick slab

40lb bags: 22

60 lb bags: 15

80 lbs bags: 11

### How many bags of concrete do I need for a 4×4 slab

The square footage for the 4×4 slab is 16.

No. of bags of Concrete for a 4-inch thick slab

40 lb bags: 20

60 lb bags: 13

80 lb bags: 10

No. of bags of Concrete for 6 inch-thick slab

40lb bags: 29

60 lb bags: 20

80 lbs bags: 15

### How many bags of concrete do I need for a 4×5 slab

The square footage for the 4×5 slab is 20.

No. of bags of Concrete for a 4-inch thick slab

40 lb bags: 24

60 lb bags: 16

80 lb bags: 12

No. of bags of Concrete for 6 inch-thick slab

40lb bags: 37

60 lb bags: 24

80 lbs bags: 18

### How many bags of concrete do I need for a 4×6 slab

The square footage for the 4×6 slab is 24.

No. of bags of Concrete for a 4-inch thick slab

40 lb bags: 29

60 lb bags: 20

80 lb bags: 15

No. of bags of Concrete for 6 inch-thick slab

40lb bags: 44

60 lb bags: 29

80 lbs bags: 22

### How many bags of concrete do I need for a 4×8 slab

No. of bags of Concrete for a 4-inch thick slab

40 lb bags: 39

60 lb bags: 26

80 lb bags: 20

No. of bags of Concrete for 6 inch-thick slab

40lb bags: 59

60 lb bags: 39

80 lbs bags: 29

### How many bags of concrete do I need for a 4×12 slab

No. of bags of Concrete for a 4-inch thick slab

40 lb bags: 59

60 lb bags: 39

80 lb bags: 29

No. of bags of Concrete for 6 inch-thick slab

40lb bags: 88

60 lb bags: 59

80 lbs bags: 44

### How many bags of concrete do I need for a 5×5 slab

No. of bags of Concrete for a 4-inch thick slab

40 lb bags: 31

60 lb bags: 20

80 lb bags: 15

No. of bags of Concrete for 6 inch-thick slab

40lb bags: 46

60 lb bags: 31

80 lbs bags: 23

### How many bags of concrete do I need for a 5×10 slab

No. of bags of Concrete for a 4-inch thick slab

40 lb bags: 61

60 lb bags: 41

80 lb bags: 31

No. of bags of Concrete for 6 inch-thick slab

40lb bags: 92

60 lb bags: 61

80 lbs bags: 46

### How many bags of concrete do I need for a 6×4 slab

No. of bags of Concrete for a 4-inch thick slab

40 lb bags: 29

60 lb bags: 20

80 lb bags: 15

No. of bags of Concrete for 6 inch-thick slab

40lb bags: 44

60 lb bags: 29

80 lbs bags: 22

### How many bags of concrete do I need for a 6×6 slab

No. of bags of Concrete for a 4-inch thick slab

40 lb bags: 44

60 lb bags: 29

80 lb bags: 22

No. of bags of Concrete for 6 inch-thick slab

40lb bags: 66

60 lb bags: 44

80 lbs bags: 33

### How many bags of concrete do I need for a 7×7 slab

No. of bags of Concrete for a 4-inch thick slab

40 lb bags: 60

60 lb bags: 40

80 lb bags: 30

No. of bags of Concrete for 6 inch-thick slab

40lb bags: 90

60 lb bags: 60

80 lbs bags: 45

### How many bags of concrete do I need for 8×8 slab

No. of bags of Concrete for a 4-inch thick slab

40 lb bags: 78

60 lb bags: 52

80 lb bags: 39

No. of bags of Concrete for 6 inch-thick slab

40lb bags: 117

60 lb bags: 78

80 lbs bags: 59

### How many bags of concrete do I need for a 8×10 slab

No. of bags of Concrete for a 4-inch thick slab

40 lb bags: 98

60 lb bags: 65

80 lb bags: 49

No. of bags of Concrete for 6 inch-thick slab

40lb bags: 147

60 lb bags: 98

80 lbs bags: 73

### How many bags of concrete do I need for a 9×9 slab

No. of bags of Concrete for a 4-inch thick slab

40 lb bags: 99

60 lb bags: 66

80 lb bags: 50

No. of bags of Concrete for 6 inch-thick slab

40lb bags: 149

60 lb bags: 99

80 lbs bags: 74

### How many bags of concrete do I need for a 10×8 slab

No. of bags of Concrete for a 4-inch thick slab

40 lb bags: 98

60 lb bags: 65

80 lb bags: 49

No. of bags of Concrete for 6 inch-thick slab

40lb bags: 147

60 lb bags: 98

80 lbs bags: 73

### How many bags of concrete do I need for a 10×10 slab

No. of bags of Concrete for a 2-inch thick slab

40 lb bags: 61

60 lb bags: 41

80 lb bags: 31

No. of bags of Concrete for a 4-inch thick slab

40 lb bags: 122

60 lb bags: 81

80 lb bags: 61

No. of bags of Concrete for 6 inch-thick slab

40lb bags: 183

60 lb bags: 122

80 lbs bags: 92

### How many bags of concrete do I need for a 10×12 slab

No. of bags of Concrete for a 4-inch thick slab

40 lb bags: 147

60 lb bags: 98

80 lb bags: 73

No. of bags of Concrete for 6 inch-thick slab

40lb bags: 220

60 lb bags: 147

80 lbs bags: 110

### How many bags of concrete do I need for a 10×15 slab

No. of bags of Concrete for a 4-inch thick slab

40 lb bags: 183

60 lb bags: 122

80 lb bags: 92

No. of bags of Concrete for 6 inch-thick slab

40lb bags: 275

60 lb bags: 183

80 lbs bags: 138

### How many bags of concrete do I need for a 10×20 slab

No. of bags of Concrete for a 4-inch thick slab

40 lb bags: 244

60 lb bags: 163

80 lb bags: 122

No. of bags of Concrete for 6 inch-thick slab

40lb bags: 367

60 lb bags: 244

80 lbs bags: 183

### How many bags of concrete do I need for a 12×8 slab

No. of bags of Concrete for a 4-inch thick slab

40 lb bags: 117

60 lb bags: 78

80 lb bags: 59

No. of bags of Concrete for 6 inch-thick slab

40lb bags: 176

60 lb bags: 117

80 lbs bags: 88

### How many bags of concrete do I need for a 12×10 slab

No. of bags of Concrete for a 4-inch thick slab

40 lb bags: 147

60 lb bags: 98

80 lb bags: 73

No. of bags of Concrete for 6 inch-thick slab

40lb bags: 220

60 lb bags: 147

80 lbs bags: 110

### How many bags of concrete do I need for a 12×12 slab

No. of bags of Concrete for a 4-inch thick slab

40 lb bags: 176

60 lb bags: 117

80 lb bags: 88

No. of bags of Concrete for 6 inch-thick slab

40lb bags: 264

60 lb bags: 176

80 lbs bags: 132

### How many bags of concrete do I need for a 12×16 slab

No. of bags of Concrete for a 4-inch thick slab

40 lb bags: 235

60 lb bags: 156

80 lb bags: 114

No. of bags of Concrete for 6 inch-thick slab

40lb bags: 352

60 lb bags: 235

80 lbs bags: 176

### How many bags of concrete do I need for a 12×20 slab

No. of bags of Concrete for a 4-inch thick slab

40 lb bags: 293

60 lb bags: 196

80 lb bags: 147

No. of bags of Concrete for 6 inch-thick slab

40lb bags: 440

60 lb bags: 293

80 lbs bags: 220

### How many bags of concrete do I need for a 12×24 slab

No. of bags of Concrete for a 4-inch thick slab

40 lb bags: 352

60 lb bags: 235

80 lb bags: 176

No. of bags of Concrete for 6 inch-thick slab

40lb bags: 528

60 lb bags: 352

80 lbs bags: 264

### How many bags of concrete do I need for a 15×15 slab

No. of bags of Concrete for a 4-inch thick slab

40 lb bags: 275

60 lb bags: 183

80 lb bags: 138

No. of bags of Concrete for 6 inch-thick slab

40lb bags: 413

60 lb bags: 275

80 lbs bags: 206

### How many bags of concrete do I need for a 16×16 slab

No. of bags of Concrete for a 4-inch thick slab

40 lb bags: 313

60 lb bags: 209

80 lb bags: 156

No. of bags of Concrete for 6 inch-thick slab

40lb bags: 469

60 lb bags: 313

80 lbs bags: 235

### How many bags of concrete do I need for a 20×20 slab

No. of bags of Concrete for a 4-inch thick slab

40 lb bags: 489

60 lb bags: 326

80 lb bags: 244

No. of bags of Concrete for 6 inch-thick slab

40lb bags: 733

60 lb bags: 489

80 lbs bags: 367

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