How much concrete do i need for a 20×20×4 slab? To calculate the amount of concrete needed for a slab, you’ll need to multiply the length, width, and thickness of the slab (in feet) to find its volume in cubic feet, and then convert that to cubic yards (since concrete is typically sold by the cubic yard). For your 20x20x4 slab:

1. Calculate the volume in cubic feet: Volume = Length (20 ft) x Width (20 ft) x Thickness (4/12 ft, since 4 inches is 1/3 of a foot), Volume = 20 ft x 20 ft x (4/12) ft = 133.33 cubic feet.

2. Convert to cubic yards: Since there are 27 cubic feet in 1 cubic yard, divide the volume by 27: 133.33 cubic feet ÷ 27 = approximately 4.94 cubic yards.

So, you will need approximately 4.94 cubic yards of concrete for a 20x20x4 slab. It’s a good idea to order a bit more than this to account for any spillage or variations in the slab thickness during pouring.

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

Regardless of size you need to calculate the volume of concrete in cubic yard before ordering the mixed concrete. Volume is calculated by multiplying length, width and depth of slab. In this article we have to calculate required quantity of concrete in cubic yard for a 20×20 (400 sq ft) slab at 4 inch, 5 inch or 6 inch thick.

Generally standard thickness of slab is 4 inch thick in normal conditions, if 20×20 slab have heavy traffic and heavy load, you should take depth 5 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 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.

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 feer), so 1 cubic yard is equal to 27 cubic feet.

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

**To determine the how much concrete do I need for a 20×20×4 slab solve in following steps:-**

Step 1 :- calculate the volume in cubic feet:- we have given 20×20 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 = 20′×20′×0.33′ = 132 cubic foot.

Step 2 :- converting cubic feet into cubic yard:- now converting into cubic yard, you should divide it by 27, because 1 cubic yard = 27 cubic foot, so volume of concrete you needed for 20×20 slab at 4 inch thick in cubic yard = 132/27 = 4.88 cubic yard.

Step 3 :- Add 10% extra :- considering extra 10% wastage during mixing and pouring, so 10% of 4.88 cubic yard = 0.488, add 4.88 + 0.488 = 5.368 cubic yard.

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

For a 20×20×4 slab, generally, you will need 4.88 cubic yards or 132 cubic feet or either 294- 60lb or 220- 80lb or 440- 40lb bags of premixed concrete. Always you should purchase 5 to 10% more premixed than required. 4″ thick slab of 20×20 is ideal in normal load or standard condition for making sidewalks, curbs, steps, ramp, walkway and patio

**How many yards of concrete do i need for a 20×20×4 slab**

At 4 inches thick, for a 20×20×4 slab, you would need 4.88 cubic yards or 132 cubic feet of concrete. If you measure in concrete bag then either 220 80-Pound, 294 60-pound, 352 50-pound, or 440 40-pound bags of premixed concrete will be required.

For a 20×20×4 slab, generally, you will need approximately 4.88 cubic yards of premixed concrete. Math’s calculation:- 1) square footage of slab = 20×20 = 400 sq ft, 2) 4″ thickness in inches = 4÷12 = 0.33 feet, 3) volume of slab in cubic feet = 400×0.33 = 132 cubic feet, and 4) volume of slab in cubic yards = 132÷27 = 4.88 cubic yards. Thus, you will need 4.88 cubic yards of premixed concrete for a 20×20 slab at 4 inches thick.

**How many cubic feet of concrete do I need for a 20×20×4 slab**

For a 20×20×4 slab, generally, you will need approximately 132 cubic feet of premixed concrete. Math’s calculation:- 1) square footage of slab = 20×20 = 400 sq ft, 2) 4″ thickness in inches = 4÷12 = 0.33 feet, 3) volume of slab in cubic feet = 400×0.33 = 132 cubic feet. Thus, you will need 132 cubic feet of premixed concrete for a 20×20 slab at 4 inches thick.

**How many bags of concrete do I need for a 20×20×4 slab**

To determine how many bags of concrete you will need, divide the total cubic yards or cubic feet needed by the yields.

We know concrete bag available in 40lb, 60lb, 80lb and 90lb. 40lb bag of concrete yields about 0.011 cubic yards or 0.30 cubic feet.60lb bag of concrete yields about 0.017 cubic yards or 0.45 cubic feet. 80lb bag of concrete yields about 0.022 cubic yards or 0.60 cubic feet and 90lb bag of concrete yields about 0.025 cubic yards or 0.68 cubic feet.

For a 20×20×4 slab, generally, you will need either 294- 60lb or 220-80lb bags of premixed concrete. Math’s calculation:- 1) square footage of slab = 20×20 = 400 sq ft, 2) 4″ thickness in inches = 4÷12 = 0.33 feet, 3) volume of slab in cubic feet = 400×0.33 = 132 cubic feet, and 4) No. of 60lb bags = 132÷0.45 = 294 bags, no. of 80lb bags = 132÷0.60 = 220 bags. Thus, you will need either 294- 60lb or 220-80lb bags of premixed concrete for a 20×20 slab at 4 inches thick.

At 4 inches thick, for a 20×20×4 slab, you would need 4.88 cubic yards or 132 cubic feet of concrete. If you measure in concrete bag then either 220 80-Pound, 294 60-pound, 352 50-pound, or 440 40-pound bags of premixed concrete will be required.

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**Conclusions:-**

For a 20×20×4 slab, generally, you will need approximately 4.88 cubic yards or 132 cubic feet or either 294- 60lb or 220-80lb bags of premixed concrete. Always you should purchase 5 to 10% more premixed than required.