The cubic yards of concrete do you need for a 20×20×4 slab depends on slab dimension and thickness of slab. Here is slab dimension is 20 feet in length, 20 feet in width and 4 inches thick. To calculate the amount of concrete needed for a slab, you multiply the length, width, and depth (thickness) in feet and then convert to yards.

How many yards of concrete for a 20×20 slab? In general, for a 20×20 slab, you’ll need about 5 cubic yards of concrete at 4″ thick, 3.7 cubic yards of concrete at 3″ thick, 6.17 cubic yards of concrete at 5″ thick, and 7.41 cubic yards of concrete at 6″ thick.

In United States, based on Imperial and US customary measurement system, a cubic yard is volume of concrete that measures 1 yard (3 feet) deep, 1 yard (3 feet) tall, and 1 yard (3 feet) wide, this makes 27 cubic feet (3’×3’×3′) per cubic yard of concrete.

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 yards of concrete do I need for a 20×20×4 slab**

To calculate the amount of concrete needed for a slab, you multiply the length, width, and depth (thickness) in feet and then convert to yards.

**Here’s are calculation steps for how much concrete do I need for a 20×20×4 slab:-**

1. Convert thickness in feet: Divide the thickness in inches by 12 to get into feet, like 4/12 = 0.333′

2. Estimate cubic feet of concrete: To calculate the volume of concrete needed for a 20x20x4 slab, multiply the length, width, and depth (thickness) in feet, like 20 ft (length) × 20 ft (width) × 4/12 ft (depth) = 133.33 cubic feet of concrete.

3. Estimate cubic yards of concrete: Divide the cubic feet by 27 (since 1 cubic yard = 27 cubic feet), like 133.33/27 = 4.94 yards. This will give you the total yards of concrete needed.

4. Estimate no. of 80 lb bags of concrete: Divide cubic feet of concrete by yields of a 80 lb bags of concrete, like 133.33/0.60 = 223 bags

5. Estimate no. of 60 lb bags of concrete: Divide cubic feet of concrete by yields of a 60 lb bags of concrete, like 133.33/0.45 = 297 bags

6. Estimate no. of 40 lb bags of concrete: Divide cubic feet of concrete by yields of a 40 lb bags of concrete, like 133.33/0.30 = 445 bags.

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

In general, for a 20×20 slab you’ll need exactly 4.94 cubic yards, or 133.33 cubic feet, or 223 x 80 lb bags of concrete at 4″ thick, while at 6″ thickness, you’ll need exactly 7.41 cubic yards, or 200 cubic feet, or 334 x 80 lb bags of concrete for a 20×20 slab.

Likewise, for a 20×20 slab you’ll need exactly 3.7 cubic yards, or 100 cubic feet, or 167 x 80 lb bags of concrete at 3″ thick, while at 5″ thickness, you’ll need exactly 6.17 cubic yards, or 167 cubic feet, or 278 x 80 lb bags of concrete for a 20×20 slab.

**How many bags of concrete for 20×20 slab**

In general, for a 20×20 slab you’ll need 223 x 80 lb or 297 x 60 lb bags of concrete at 4″ thick, 167 x 80 lb or 223 x 60 lb bags of concrete at 3″ thick, 278 x 80 lb or 371 x 60 lb bags of concrete at 5″ thick, and 334 x 80 lb or 445 x 60 lb bags of concrete at 6″ thick.

**Conclusion:**

Typically for a 20x20x4 slab you’ll need exactly 4.94 cubic yards, or 133.33 cubic feet, or either 223 x 80 lb bags, 297 × 60 lb bags, or 445 × 40 lb bags of concrete. It’s a good idea to order a little extra to account for potential spillage and to ensure you have enough to complete the project.