# How much concrete do i need for a 20×40 slab

How much concrete do i need for a 20×40 slab | how much concrete do i need for a 20×40 slab | how many cubic feet of concrete do i need for a 20×40 slab | concrete calculator formula.

A 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, ready mix concrete are prepaired at construction site or delivered, by manually mix or by mixer machine or RMC truck.

Generally for larger projects, Ready mixed concrete is calculated by the yard, which is is good for making Large patios, driveways, pool decks and more, Foundation slabs for a house, Parking lots or commercial sidewalks.

Larger jobs such as driveways, roadway, and larger slab are simple easier to complete when ordering concrete by the cubic yards, rather than trying to mix a concrete bag after bag by hand. But for smaller jobs, like a walkway, modest patio or footings, you should calculate the number of concrete bags instead. Bagged concrete is ideal for Pouring small slabs for sidewalks or patios, setting posts for fences or mailboxes, making repairs to foundation walls, walkways or steps, pouring small curbs, steps, or ramps
Footings for decks, pergolas, walls and more.

If you want to install 20×40 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 20 foot by 40 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 20×40 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 20×40 (800 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 much concrete do i need for a 20×40 slab

How to calculate concrete by yard based on concrete calculator formula, which are following:- 1) determine how thick you want the concrete, 2) measure the length and width that you’d like to cover, 3) multiply the length by the width to determine square footage, 4) convert the thickness from inches to feet, 5)
multiply the thickness in feet by the square footage to determine cubic feet, and 6) convert cubic feet to cubic yards by multiplying by 0.037. Always add 10% extra which would be wastage during mixing and pouring.

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Concrete quantity at 3 inches thick

Here you have 20×40 slab at 3 inches thick, now calculate concrete quantity with the help of concrete calculator formula as:-

1) square footage = 20×40 = 800 sq ft

2) thickness in feet = 3÷12 = 0.25 feet

3) concrete quantity in cubic feet = 800 × 0.25 = 200 cubic feet

4) concrete quantity in cubic yards = 200 × 0.037 = 7.4 cubic yards.

Concrete quantity at 4 inches thick

Here you have 20×40 slab at 4 inches thick, now calculate concrete quantity with the help of concrete calculator formula as:-

1) square footage = 20×40 = 800 sq ft

2) thickness in feet = 4÷12 = 0.33 feet

3) concrete quantity in cubic feet = 800 × 0.33 = 264 cubic feet

4) concrete quantity in cubic yards = 264 × 0.037 = 9.8 cubic yards.

Concrete quantity at 5 inches thick

Here you have 20×40 slab at 5 inches thick, now calculate concrete quantity with the help of concrete calculator formula as:-

1) square footage = 20×40 = 800 sq ft

2) thickness in feet = 5÷12 = 0.416 feet

3) concrete quantity in cubic feet = 800 × 0.416 = 333 cubic feet

4) concrete quantity in cubic yards = 333 × 0.037 = 12.33 cubic yards.

Concrete quantity at 6 inches thick

Here you have 20×40 slab at 6 inches thick, now calculate concrete quantity with the help of concrete calculator formula as:-

1) square footage = 20×40 = 800 sq ft

2) thickness in feet = 6÷12 = 0.5 feet

3) concrete quantity in cubic feet = 800 × 0.5 = 400 cubic feet

4) concrete quantity in cubic yards = 400 × 0.037 = 14.82 cubic yards.

How much concrete do i need for a 20×40 slab?, You will need approximately 9.8 cubic yards (264 cubic feet) of ready mix concrete for a 20’×40′ slab at 4 inches thick, 7.4 cubic yards (200 cubic feet) of concrete at 3 inches thick, 12.33 cubic yards (333 cubic feet) of concrete at 5 inches thick, and 14.82 cubic yards (400 cubic feet) of concrete at 6 inches thick.

### How much concrete do i need for a 20×40 slab at 4″ thick

As per general practices, you will need approximately 9.8 cubic yards, or 264 cubic feet, or 7.47m3 of ready mix concrete for a 20×40 slab at 4 inches thick. Maths calculation:- 1) 20×40 = 800 square footage, 2) 4÷12 = 0.33 feet, 3) 800 × 0.33 = 264 cubic feet, and 4) 264×0.037 = 9.8 cubic yards.

#### How many yards of concrete do I need for a 20×40 slab

As per general practices, generally you will need approximately 9.8 cubic yards or 264 cubic feet or 7.47m3 of ready mix concrete for a 20×40 slab at 4 inches thick. At 5 inches thick, for a 20’×40′ slab, 12.33 cubic yards or 333 cubic feet or 9.42m3 of ready mix concrete are required, while at 6 inches thick, 14.82 cubic yards or 400 cubic feet or 11.33m3 of ready mix concrete are necessary.

#### How many cubic feet of concrete do I need for a 20×40 slab

As per general practices, generally you will need 264 cubic feet of ready mix concrete for a 20×40 slab at 4 inches thick. At 5 inches thick, for a 20’×40′ slab, 333 cubic feet of premixed concrete are required, while at 6 inches thick, 400 cubic feet of premixed concrete are necessary.

### How many yards of concrete do i need for a 20×40 slab at 4″ thick

You will need approximately 9.8 cubic yards or 264 cubic feet of ready mix concrete for a 20’×40′ slab at 4 inches thick. Maths calculation:- 1) 20×40 = 800 square footage, 2) 4÷12 = 0.33 feet, 3) 800 ×0.33 = 264 cubic feet, and 4) 264 × 0.037 = 9.8 cubic yards.

#### How many yards of concrete do i need for a 20×40 slab at 5″ thick

You will need approximately 12.33 cubic yards or 333 cubic feet of ready mix concrete for a 20’×40′ slab at 5 inches thick. Maths calculation:- 1) 20×40 = 800 square footage, 2) 5÷12 = 0.416 feet, 3) 800 ×0.416 = 333 cubic feet, and 4) 333× 0.037 = 12.33 cubic yards.

#### How many yards of concrete do i need for a 20×40 slab at 6″ thick

You will need approximately 14.82 cubic yards or 400 cubic feet of ready mix concrete for a 20’×40′ slab at 6 inches thick. Maths calculation:- 1) 20×40 = 800 square footage, 2) 6÷12 = 0.50 feet, 3) 800 ×0.5 = 400 cubic feet, and 4) 400× 0.037 = 14.82 cubic yards.

#### How many yards of concrete do i need for a 20×40 slab at 3″ thick

You will need approximately 7.4 cubic yards or 200 cubic feet of ready mix concrete for a 20’×40′ slab at 3 inches thick. Maths calculation:- 1) 20×40 = 800 square footage, 2) 3÷12 = 0.25 feet, 3) 800 ×0.25 = 200 cubic feet, and 4) 200× 0.037 = 7.4 cubic yards.

### How many cubic feet of concrete do I need for a 20×40 slab at 3″ thick

As per general practices, generally you will need 200 cubic feet or 7.4 yards of ready mix concrete for a 20×40 slab at 3 inches thick. Maths calculation:- 1) 20×40 = 800 square footage, 2) 3÷12 = 0.25 feet, 3) 800 ×0.25 = 200 cubic feet.

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#### How many cubic feet of concrete do I need for a 20×40 slab at 4″ thick

As per general practices, generally you will need 264 cubic feet or 9.8 yards of ready mix concrete for a 20×40 slab at 4 inches thick. Maths calculation:- 1) 20×40 = 800 square footage, 2) 4÷12 = 0.33 feet, 3) 800 ×0.33 = 264 cubic feet.

#### How many cubic feet of concrete do I need for a 20×40 slab at 5″ thick

As per general practices, generally you will need 333 cubic feet or 12.33 yards of ready mix concrete for a 20×40 slab at 5 inches thick. Maths calculation:- 1) 20×40 = 800 square footage, 2) 5÷12 = 0.416 feet, 3) 800 ×0.416 = 333 cubic feet.

#### How many cubic feet of concrete do I need for a 20×40 slab at 6″ thick

As per general practices, generally you will need 400 cubic feet or 14.82 yards of ready mix concrete for a 20×40 slab at 6 inches thick. Maths calculation:- 1) 20×40 = 800 square footage, 2) 6÷12 = 0.50 feet, 3) 800 ×0.5 = 400 cubic feet.

Conclusions:-

You will need approximately 9.8 cubic yards (264 cubic feet) of ready mix concrete for a 20×40 slab at 4 inches thick, 7.4 cubic yards (200 cubic feet) of concrete at 3 inches thick, 12.33 cubic yards (333 cubic feet) of concrete at 5 inches thick, and 14.82 cubic yards (400 cubic feet) of concrete at 6 inches thick.