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

How many bags of concrete do i need for a 4×8 slab | how much concrete do i need for a 4×8 slab | how many cubic yards of concrete do i need for a 4×8 slab | how many cubic feet of concrete do i need for a 4×8 slab.

A bag of ready mix concrete is made of blended mix of Portland cement, gravel (coarse aggregate), sand (fine aggregate) and other approved ingredients or admixture. Different admixture are added to improve its workability. In US, dry ready mix concrete are packed in different bag size and weight in pounds such as smaller bag of 40lb (pounds) and 50lb (pounds), medium are of 60lb (pounds) bag, and larger are of 80lb and 90lb bag.

If you want to install 4×8 concrete slab, first thing is to know about depth of slab and square footage of slab. Regardless of premixed concrete bag size, you need to figure out the volume of concrete in cubic yards or in cubic feet or in cubic meters or in RMC truckload before ordering the mixed concrete.

Volume of concrete slab is calculated by multiplying length, width and depth of slab. Here you have given a slab of area 4 foot by 8 foot and recommended depth of slab is 4 inches. What is thickness of slab?, Generally depth of slab is kept between 3″ to 6″, but we recommend 4 inches depth of slab is better for normal weight condition. Although it’s depend on, is this a slab on the ground or it is elevated, rules differ for both, since failure of ground slab would not kill anyone whereas failure of an elevated slab could.

As per general practices and thumb rules involves the safety factor that deciding the thickness of slab. 4 inches thick depth is generally for ground slab, for heavy traffic and heavy load, you should take depth 5 or 6 inches thick and for an elevated slab generally thickness should be 5″ to 6″, and 4 inch thick is also made to use in normal weight conditions.

Standard thickness of slab is kept 4 inches thick in normal weight conditions, if 4×8 slab have heavy traffic and heavy load, you should take depth of 5 or 6 inches thick. In this article we have to figure out quantity of concrete required in cubic yards, in cubic feet and cubic meters for a 4×8 (32 sq ft) slab at 4 inches, 5 inches or 6 inches thick.

A typical Ready mix concrete in dry condition is weigh about 133lb (pounds) per cubic foot, or 3600lb (pounds) per cubic yard, or which is approximately equal as 2136kg per cubic meter. The weight of ready mix concrete is determined by its density, which can vary based on the amount of gravel, sand, cement, small amount of water, and air in the mix.

In United States, based on Imperial and US customary measurement system, 1 cubic yard of concrete is unit of measurement of volume , which is visually represented by 3 feet long by 3 feet wide by 3 feet depth, so, 3’×3’× 3′ = 27 cubic feet, so 1 cubic yard is equal to 27 cubic feet.

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

To determine how many bags of concrete do I need for a 4×8 slab, you can solve in following steps:-

Step 1 :- Calculate the volume in cubic feet:- You have given 4×8 slab (length × width), consider it is 4 inches thick, 4 inch = 0.33 feet, to calculate the volume of slab, you need to multiply all dimensions, such that = 4′×8′× 0.33′ = 10.56 cubic feet, at 5 inch thick, volume of slab is 4′×8′× 0.416 = 13.3 cubic feet, at 6 inch thick, volume of slab is 4′×8′× 0.5 = 16 cubic feet, at 3 inch thick, volume of slab is 4′×8′× 0.25 = 8 cubic feet, and at 2 inch thick, volume of slab is 4′×8′× 0.166 = 5.3 cubic feet.

Step 2 :- Converting cubic feet into cubic yards:- for converting cubic feet into cubic yards, you should divide it by 27, so volume of concrete you needed for 4×8 slab at 4 inch thick in cubic yards = 10.56/27 = 0.39 cubic yards, at 5 inch thick = 13.3/27 = 0.49 cubic yards, at 6 inch thick = 16/27 = 0.59 cubic yards, at 3 inch thick = 8/27 = 0.30 cubic yards, and at 2 inch thick = 5.3/27 = 0.20 cubic yards.

Step 3:- add 10% extra which would be wastage during mixing and pouring.

Step 4:- to determine how many bags of concrete you will need, divide the total cubic yardage by the one bag yields, as you know premixed bag of concrete available in 40lb, 60lb & 80lb. 40lb bag of concrete yields about 0.011 cubic yards, 60lb bag of concrete yields about 0.017 cubic yards and 80lb bag of concrete yields about 0.022 cubic yards.

Number of bags of concrete for a 4×8 slab at 4 inches thick

● Number of 80lb bag of concrete = 0.39 ÷ 0.022 = 18 bags,

● No. of 60lb bag of concrete = 0.39 ÷ 0.017 = 23 bags, and

● No. of 40lb bag of premixed concrete = 0.39 ÷ 0.011 = 36 bags.

Number of bags of concrete for a 4×8 slab at 5 inches thick

● Number of 80lb bag of premixed concrete = 0.59 ÷ 0.022 = 23 bags,

● No. of 60lb bag of premixed concrete = 0.59 ÷ 0.017 = 29 bags, and

● No. of 40lb bag of premixed concrete = 0.59÷ 0.011 = 45 bags.

Number of bags of concrete for a 4×8 slab at 6 inches thick

● Number of 80lb bag of premixed concrete = 0.59 ÷ 0.022 = 27 bags,

● No. of 60lb bag of premixed concrete = 0.59 ÷ 0.017 = 35 bags, and

● No. of 40lb bag of premixed concrete = 0.59 ÷ 0.011 = 54 bags.

Number of bags of concrete for a 4×8 slab at 3 inches thick

● Number of 80lb bag of premixed concrete = 0.30 ÷ 0.022 = 14 bags,

● No. of 60lb bag of premixed concrete = 0.30 ÷ 0.017 = 18 bags, and

● No. of 40lb bag of premixed concrete = 0.30 ÷ 0.011 = 28 bags.

Number of bags of concrete for a 4×8 slab at 2 inches thick

● Number of 80lb bag of premixed concrete = 0.20 ÷ 0.022 = 9 bags,

● No. of 60lb bag of premixed concrete = 0.20 ÷ 0.017 = 12 bags, and

● No. of 40lb bag of premixed concrete = 0.20 ÷ 0.011 = 19 bags.

How many bags of concrete do I need for a 4×8 slab?”, You will need approximately either 23 bags of 60lb, or 18 bags of 80lb, or 36 bags of 40lb of premixed concrete for a 4’×8′ slab at 4 inches thick. At 5 inches thick slab of 4’×8′, either 29 bags of 60lb, or 23 bags of 80lb, or 45 bags of 40lb premixed concrete are required, while at 6 inches thick slab, either 35 bags of 60lb, or 27 bags of 80lb, or 54 bags of 40lb premixed concrete are necessary.

### How much concrete do I need for a 4×8 slab

As per general practices, generally you will need approximately 0.39 cubic yards or 10.56 cubic feet or 0.30 m3 (either 23 bags of 60lb or 18 bags of 80lb) of premixed concrete for a 4’×8′ slab at 4 inches thick. At 5 inches thick, for a 4’×8′ slab, 0.49 cubic yards or 13.3 cubic feet or 0.38 m3 (either 29 bags of 60lb or 23 bags of 80lb) of premixed concrete are required, while at 6 inches thick, 0.59 cubic yards or 16 cubic feet or 0.45 m3 (either 35 bags of 60lb or 27 bags of 80lb) of premixed concrete are necessary.

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

As per general practices, you will need 0.39 cubic yards of premixed concrete for a 4×8 slab at 4 inches thick. At 5 inches thick, for a 4’×8′ slab, 0.49 cubic yards of premixed concrete are required, while at 6 inches thick, 0.59 cubic yards of premixed concrete are necessary.

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

As per general practices, generally you will need 10.56 cubic feet of premixed concrete for a 4×8 slab at 4 inches thick. At 5 inches thick, for a 4’×8′ slab, 13.3 cubic feet of premixed concrete are required, while at 6 inches thick, 16 cubic feet of premixed concrete are necessary.

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

As per general practices, generally you will need approximately either 23 bags of 60lb or 18 bags of 80lb, or 36 bags of 40lb (0.39 cubic yards or 10.56 cubic feet or 0.30 m3) of premixed concrete for a 4×8 slab at 4 inches thick

#### How many bags of concrete do I need for a 4×8 slab at 5″ thick

As per general practices, generally you will need approximately either 29 bags of 60lb or 23 bags of 80lb, or 45 bags of 40lb (0.49 cubic yards or 13.3 cubic feet or 0.376 m3) of premixed concrete for a 4×8 slab at 5 inches thick

#### How many bags of concrete do I need for a 4×8 slab at 6″ thick

As per general practices, generally you will need approximately either 35 bags of 60lb or 27 bags of 80lb, or 54 bags of 40lb (0.59 cubic yards or 16 cubic feet or 0.45 m3) of premixed concrete for a 4×8 slab at 6 inches thick.

#### How many bags of concrete do I need for a 4×8 slab at 3″ thick

As per general practices, generally you will need approximately either 18 bags of 60lb or 14 bags of 80lb, or 28 bags of 40lb (0.30 cubic yards or 8 cubic feet or 0.23 m3) of premixed concrete for a 4×8 slab at 3 inches thick.

#### How many bags of concrete do I need for a 4×8 slab at 2″ thick

As per general practices, generally you will need approximately either 12 bags of 60lb or 9 bags of 80lb, or 19 bags of 40lb (0.20 cubic yards or 5.3 cubic feet or 0.15 m3) of premixed concrete for a 4×8 slab at 2 inches thick.

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### How many 80lb bags of concrete do I need for a 4×8 slab

As per general practices, generally you will need approximately 18 bags of 80lb (pounds) of premixed concrete for a 4×8 slab at 4 inches thick, 23 bags of 80lb at 5″ thick, 27 bags of 80lb at 6″ thick, 14 bags of 80lb at 3″ thick, and 9 bags of 80lb at 2″ thick.

#### How many 60lb bags of concrete do I need for a 4×8 slab

As per general practices, generally you will need approximately 23 bags of 60lb (pounds) of premixed concrete for a 4×8 slab at 4 inches thick, 29 bags of 60lb at 5″ thick, 35 bags of 60lb at 6″ thick, 18 bags of 60lb at 3″ thick, and 12 bags of 60lb at 2″ thick.

#### How many 40lb bags of concrete do I need for a 4×8 slab

As per general practices, generally you will need approximately 36 bags of 40lb (pounds) of premixed concrete for a 4×8 slab at 4 inches thick, 45 bags of 40lb at 5″ thick, 54 bags of 40lb at 6″ thick, 28 bags of 40lb at 3″ thick, and 19 bags of 40lb at 2″ thick.

Conclusions:-

As per general practices, generally you will need approximately either 23 bags of 60lb or 18 bags of 80lb, or 36 bags of 40lb (0.39 cubic yards or 10.56 cubic feet or 0.30 m3) of premixed concrete for a 4×8 slab at 4 inches thick.