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 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 | How many bags of concrete do I need for a 4×8 slab at 4″ thick | How many bags of concrete do I need for a 4×8 slab at 5″ thick | How many bags of concrete do I need for a 4×8 slab at 6″ thick | how many m3 of concrete do I need for a 4×8 slab.

A bag of concrete ready mix made of blended mix of Portland cement, sand gravel and other approved ingredient or admixture, generally, dry ready mix concrete are available in different bag size and weight condition such as 40lb, 60lb bag, 80lb bag, 90lb bag and etc.

Regardless of size you need to calculate the volume of concrete in cubic yard or in cubic feet or in cubic meter or in rmc truck before ordering the mixed concrete. Volume is calculated by multiplying length, width and depth of slab. Here you have given a slab of 4 feet in length and 8 feet in wide, what is thickness of slab?, 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.

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

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

Generally standard thickness of slab is 4 inch thick in normal conditions, if 4×8 slab have heavy traffic and heavy load, you should take depth 5 or 6 inch thick. In this article we have to calculate required quantity of concrete in cubic yard & in cubic feet and cubic meter for a 4×8 (32 sq ft) slab at 4 inch, 5 inch or 6 inch thick.

Weight of Ready mix concrete in dry condition is about 133 lbs per cubic foot, 3600 lbs per cubic yard, or approximately equal as 2136 kg per cubic meter. The weight of concrete is determined by its density, which can vary based on the amount of aggregate, water, and air in the mix.

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In United States, based on Imperial and US customary measurement system, 1 cubic yard is unit of measurement of volume represented by 3 feet long by 3 feet wide by 3 feet depth (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 the how much concrete do I need for a 4×8 slab & how many bags of concrete do I need for this, 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 inch thick, 4 inch = 0.33 feet, to determine the volume of slab, you need to multiply all dimensions, such that = 4′×8′× 0.33′ = 10.56 cubic foot, at 5 inch thick, volume of slab is 4′×8′× 0.416 = 13.31 cubic foot and at 6 inch thick, volume of slab is 4′×8′× 0.5 = 16 cubic foot.

Step 2 :- converting cubic feet into cubic yard:- now converting into cubic yard, you should divide it by 27, so volume of concrete you needed for 4×8 slab at 4 inch thick in cubic yard = 10.55/27 = 0.391 cubic yards, at 5 inch thick = 13.31/27 = 0.493 cubic yards & at at 6 inch thick = 16/27 = 0.592 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 yards needed by the 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.

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

To determine how many bags of concrete you will need, divide the total cubic yards needed by the yields, at 4 inch thick, for a 4×8 slab you will need 0.391 yards of concrete, so number of 80lb bag of concrete = 0.391 ÷ 0.022 = 18 bags, No. of 60lb bag = 0.391 ÷ 0.017 = 23 bags & No. of 40lb bag = 0.391 ÷ 0.011 = 36 bags.

At 4 inch thick, for a 4×8 slab, you will need either twenty three 60- pounds or eighteen 80- pounds or thirty six 40- pounds bags of concrete. Thus, either 23- 60lb or 18- 80lb or 36- 40lb bags of concrete will be required for a 4×8 slab at 4″ thick.

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

To determine how many bags of concrete you will need, divide the total cubic yards needed by the yields, at 5 inch thick, for a 4×8 slab you will need 0.493 yards of concrete, so number of 80lb bag of concrete = 0.493 ÷ 0.022 = 23 bags, No. of 60lb bag = 0.493 ÷ 0.017 = 29 bags and No. of 40lb bag = 0.493 ÷ 0.011 = 45 bags.

At 5 inch thick, for a 4×8 slab, you will need either twenty nine 60- pounds or twenty three 80- pounds or forty five 40- pounds bags of concrete. Thus, either 29- 60lb or 23- 80lb or 45- 40lb bags of concrete will be required for a 4×8 slab at 5″ thick.

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

To determine how many bags of concrete you will need, divide the total cubic yards needed by the yields, at 6 inch thick, for a 4×8 slab you will need 0.592 yards of concrete, so number of 80lb bag of concrete = 0.592 ÷ 0.022 = 27 bags, No. of 60lb bag = 0.592 ÷ 0.017 = 35 bags and No. of 40lb bag = 0.592 ÷ 0.011 = 54 bags.

At 6 inch thick, for a 4×8 slab, you will need either thirty five 60- pounds or twenty seven 80- pounds or fifty four 40- pounds bags of concrete. Thus, either 35- 60lb or 27- 80lb or 54- 40lb bags of concrete will be required for a 4×8 slab at 6″ thick.

Regarding this, **“how many bags of concrete do I need for a 4×8 slab?”**, at 4 inches thick, generally you will need approximately either 23 bags of 60lb or 18 bags of 80lb of premixed concrete for a 4×8 slab, at 5 inches thick slab, either 29 bags of 60lb or 23 bags of 80lb premixed concrete are required, while at 6 inches thick slab, either 35 bags of 60lb or 27 bags of 80lb premixed concrete is necessary.

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**Conclusions**:-

At 4 inch thick, for a 4×8 slab, you will need either 23- 60-pound or 18- 80-pound or 36-40-pounds bags of concrete, while at 6-inch thick slab, either 35- 60-pound or 27- 80-pound bags are necessary and at 5 inch thick slab, either 29- 60-pound or 23- 80-pound bags of concrete will be required.