To calculate how many bags of concrete you need for an 8×8 slab, you’ll first need to determine the thickness of the slab you want. Standard concrete slabs are typically 4 inches thick, but you may want a different thickness depending on your project.

Concrete is a blended mix of Portland cement, sand, aggregate, water with approve ingredient. Cement is acts as binder or adhesive materials to bind the components of concrete all together to create workable paste. Sand acts as filler material that fills the voids and gap between components of concrete and remove the air. Aggregate, stone, or gravel used to strengthen the concrete strength.

To determine how many bags of premixed concrete you will need, divide the total cubic yards needed by the yield. Use the following yields per each bag size: A 40 pound bag yields 0.011 cubic yards, 60 pound bag yields 0.017 cubic yards, 50 pound bag yields 0.0138 cubic yards and 80 pound bag yields 0.022 cubic yards.

If you measure their yields in cubic feet, then yields per each bag size are following: A 40 pound bag yields 0.30 cubic feet, 60 pound bag yields 0.45 cubic feet, 50 pound bag yields 0.375 cubic feet and 80 pound bag yields 0.60 cubic feet.

To figure the amount of yards of concrete you will need, take the all measurements Length in feet, width in feet and thickness in inches. Convert thickness in feet. Multiply its length, width and thickness to get cubic footage. Multiply the total cubic footage by 0.037 to get total yards of concrete needed.

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

For a 8×8 slab, you would need approximately 0.782 yards (21.12 cubic feet, or either 36- 80lb, 47- 60lb bags) of concrete at 4″ thick, 0.99 yards (26.69 cubic feet, or either 45- 80lb, 60- 60lb bags) of concrete at 5″ thick, 0.59 yards (16 cubic feet, or either 27- 80lb, 36- 60lb bags) of concrete at 3″ thick, or 1.19 yards (32 cubic feet, or either 54- 80lb, 72- 60lb bags) of concrete at 6″ thick.

**How many bags of concrete do i need for a 8×8 slab at 4 inches thick**

At 4 inches thick, for a 8×8 slab you would need 0.782 cubic yards or 21.12 cubic feet of concrete. If you use premix concrete, either 36 80-Pound, 47 60-pound, 57 50-pound, or 71 40-pound bags of premixed concrete will be required.

**Let’s do calculation and proceeds following steps:**

● 4″ thickness in feet = 4/12 = 0.33′

● Volume of concrete in cubic feet = 8 × 8 × 0.33 = 21.12

● Volume of concrete in yards = 21.12 × 0.037 = 0.782 yards.

● No. of 80lb bags = 21.12/0.60 = 36 bags

● No. of 60lb bags = 21.12/0.45 = 47 bags

● No. of 50lb bags = 21.12/0.375 = 57 bags

● No. of 40lb bags = 21.12/0.30 = 71 bags

**How many bags of concrete do i need for a 8×8 slab at 5 inches thick**

At 5 inches thick, for a 8×8 slab you would need 0.99 cubic yards or 26.69 cubic feet of concrete. If you use premix concrete, either 45 80-Pound, 60 60-pound, 72 50-pound, or 89 40-pound bags of premixed concrete will be required.

**Let’s do calculation and proceeds following steps:**

● 5″ thickness in feet = 4/12 = 0.417′

● Volume of concrete in cubic feet = 8 × 8 × 0.417 = 26.69

● Volume of concrete in yards = 26.69 × 0.037 = 0.99 yards.

● No. of 80lb bags = 26.69/0.60 = 45 bags

● No. of 60lb bags = 26.69/0.45 = 60 bags

● No. of 50lb bags = 26.69/0.375 = 72 bags

● No. of 40lb bags = 26.69/0.30 = 89 bags.

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**How many bags of concrete do i need for a 8×8 slab at 3 inches thick**

At 3 inches thick, for a 8×8 slab you would need 0.59 cubic yards or 16 cubic feet of concrete. If you use premix concrete, either 27 80-Pound, 36 60-pound, 43 50-pound, or 54 40-pound bags of premixed concrete will be required.

**Let’s do calculation and proceeds following steps:**

● 3″ thickness in feet = 3/12 = 0.25′

● Volume of concrete in cubic feet = 8 × 8 × 0.25 = 16

● Volume of concrete in yards = 16 × 0.037 = 0.59 yards.

● No. of 80lb bags = 16/0.60 = 27 bags

● No. of 60lb bags = 16/0.45 = 36 bags

● No. of 50lb bags = 16/0.375 = 43 bags

● No. of 40lb bags = 16/0.30 = 54 bags.

**How many bags of concrete do i need for a 8×8 slab at 6 inches thick**

At 6 inches thick, for a 8×8 slab you would need 1.19 cubic yards or 32 cubic feet of concrete. If you use premix concrete, either 54 80-Pound, 72 60-pound, 86 50-pound, or 107 40-pound bags of premixed concrete will be required.

**Let’s do calculation and proceeds following steps:**

● 6″ thickness in feet = 6/12 = 0.5′

● Volume of concrete in cubic feet = 8 × 8 × 0.5 = 32

● Volume of concrete in yards = 32 × 0.037 = 1.19 yards.

● No. of 80lb bags = 32/0.60 = 54 bags

● No. of 60lb bags = 32/0.45 = 72 bags

● No. of 50lb bags = 32/0.375 = 86 bags

● No. of 40lb bags = 32/0.30 = 107 bags.

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**How much concrete do i need for a 20×20×4 slab**

**How many bags of concrete do i need for a 8×8 slab at 2 inches thick**

At 2 inches thick, for a 8×8 slab you would need 0.737 cubic yards or 19.92 cubic feet of concrete. If you use premix concrete, either 34 80-Pound, 45 60-pound, 54 50-pound, or 67 40-pound bags of premixed concrete will be required.

**Let’s do calculation and proceeds following steps:**

● 2″ thickness in feet = 2/12 = 0.166′

● Volume of concrete in cubic feet = 8 × 8 × 0.166 = 10.63

● Volume of concrete in yards = 10.63 × 0.037 = 0.394 yards.

● No. of 80lb bags = 10.63/0.60 = 18 bags

● No. of 60lb bags = 10.63/0.45 = 24 bags

● No. of 50lb bags = 10.63/0.375 = 29 bags

● No. of 40lb bags = 10.63/0.30 = 36 bags.

**Cost estimate for 8’×8’×4″ slab**

Pre-mixed concrete bags cost on average $3.50 per 80lb bag. There are 36 bags of 80 pound premix concrete are required for 8×8 slab at 4″ thick. Using pre-mixed bags to cover 8×8 (64 sq ft) at a depth of 4″, the estimated cost is $126 (36× $3.50 = $126).

**Cost estimate for 8’×8’×5″ slab**

Pre-mixed concrete bags cost on average $3.50 per 80lb bag. There are 45 bags of 80 pound premix concrete are required for 8×8 slab at 5″ thick. Using pre-mixed bags to cover 8×8 (64 sq ft) at a depth of 5″, the estimated cost is $157.5 (45 × $3.50 = $157.5).

**Cost estimate for 8’×8’×6″ slab**

Pre-mixed concrete bags cost on average $3.50 per 80lb bag. There are 54 bags of 80 pound premix concrete are required for 8×8 slab at 6″ thick. Using pre-mixed bags to cover 8×8 (64 sq ft) at a depth of 6″, the estimated cost is $189 (54 × $3.50 = $189).

**Conclusion:**

At 4 inches thick, for a 8×8 slab you would need 0.782 yards or 21.12 cubic feet or either 36- 80lb, 47-60lb, or 71- 40lb bags of concrete.