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How Much Does Concrete Weigh Per Square Foot?

Concrete is a very dense and heavy building material. It’s made by mixing together cement, sand and stone with water. When dry concrete is mixed with water it becomes a semi-solid similar in consistency to thick oatmeal. It’s then poured into forms where it dries, hardens and grows strong. This process is called curing and takes around 28 days to complete. So how much does concrete weigh per square foot? Because concrete is thick you can’t determine it’s weight simply by measuring square feet. You also need to consider depth. A slab of concrete 1 inch thick weighs 12.5 lb per square foot. But a slab of concrete 4 inches thick weighs 50 lb per square foot. The thicker the concrete slab the more it weighs per square foot.

Measuring the square footage of a concrete slab is easy. Simply multiply its length x width (L x W). But to figure out concrete’s weight per square foot you also have to consider its depth. The calculation is length x width x depth (L x W x D).

Concrete slabs have volume which means you have to measure them in 3 dimensions. Square foot is a 2 dimensional measurement that only measures surface area. By adding depth to the equation you turn the measurement into cubic feet instead of square feet.

When calculating how much concrete weighs do the following:

  • Multiply the length x width of the slab to calculate its square footage.
  • Then multiply that number times the slab’s thickness.

Once you know a concrete slabs cubic feet, its easy to calculate its weight. Concrete weighs 12.5 lbs per square foot @ 1 inch thick. So if you have a 6 inch thick slab (6 x 12.5 lb) it weighs 75 lb per square foot.

How Much Does A Square Foot Of Concrete Weigh?

How much concrete weighs per square foot depends on how thick the slab is. The thicker the slab the more concrete weighs per square foot of surface area.

Here’s a breakdown of how much 1 square foot of concrete weighs at different thicknesses:

  • 1 sq. ft. of concrete @ 1 inch thick weighs 12.5 pounds/sq. ft.
  • 1 sq. ft. of concrete @ 2 inch thick weighs 25 pounds/sq. ft.
  • 1 sq. ft. of concrete @ 3 inch thick weighs 37.5 pounds/sq. ft.
  • 1 sq. ft. of concrete @ 4 inch thick weighs 50 pounds/sq. ft.
  • 1 sq. ft. of concrete @ 5 inch thick weighs 62.5 pounds/sq. ft.
  • 1 sq. ft. of concrete @ 6 inch thick weighs 75 pounds/sq. ft.
  • 1 sq. ft. of concrete @ 7 inch thick weighs 87.5 pounds/sq. ft.
  • 1 sq. ft. of concrete @ 8 inch thick weighs 100 pounds/sq. ft.
  • 1 sq. ft. of concrete @ 9 inch thick weighs 112.5 pounds/sq. ft.
  • 1 sq. ft. of concrete @ 10 inch thick weighs 125 pounds/sq. ft.
  • 1 sq. ft. of concrete @ 11 inch thick weighs 137.5 pounds/sq. ft.
  • 1 sq. ft. of concrete @ 12 inch thick weighs 150 pounds/sq. ft.

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How To Calculate Concrete’s Weight Per Square Foot

The weight of concrete per square foot is calculated based on the length, width and thickness of the slab. You can’t figure out the weight of concrete without knowing how thick it is.

Concrete weighs 12.5 lb per square foot @ 1 inch thick. The thicker the slab the more concrete weighs per square foot. If you’re demolishing a slab you need to measure the surface area to determine square footage(L x W), then measure its depth.

Multiply the depth of the slab by 12.5 lbs per square foot to get the slabs actual weight per square foot based on its depth. For example, a 4 inch thick concrete slab weighs 50 lbs per square foot (12.5 lbs per sq. ft. @ 1 inch thick x 4 inches = 50 lbs per sq. ft.)

But how do you figure out how much concrete weighs per square foot if the measurements are smaller than 1 square foot or a whole inch?

To calculate how much a concrete slab weighs per square foot when the numbers get smaller I simply round up to a full square foot. For example, if I’m demolishing a 40′ 4″ slab I make it 41′ for the sake of determining weight. When filling a concrete dumpster or your truck with concrete it’s better to figure a little heavy so you don’t overload the truck.

There’s generally no need to calculate the weight of concrete to the square inch because these weights are only estimates. Things like the psi of the slab, moisture content, rebar, wire mesh, and stone size also effect its weight. We’ll get into this a bit more later in the article.

How Much Heavier Is Wet Concrete?

Concrete is a porous material that absorbs water. When concrete turns from a semi-solid paste into a rock hard structure it dries out and hardens. As concrete dries, water evaporates out leaving small tubes behind. These tubes are what gives concrete its porous structure.

A wet concrete slab weighs approximately 10% more than a dry one.

Take this difference into account when calculating the weight of a slab. This is especially important when doing demolition work or transporting broken concrete.

Calculating A Concrete Slab’s Weight

When calculating the weight of a concrete slab per square foot, per cubic foot or per cubic yard, you have to account for more than just the concrete.

Inside a concrete slab is usually reinforcing rebar and/or wire mesh. This has weight too and need to be factored into your weight measurement for the slab. Once you break the slab open you’ll be able to see what type of reinforcement the builders used. From there, find the weight of the material and factor it into your weight calculation.

Another big factor effecting concrete’s weight is water. Concrete is very absorbent and can hold a lot of water. A typical slab can weigh 10% more per square foot when wet vs when dry. Once you break open a slab you’ll be able to see how much water it’s holding. Keep in mind that although a slab may appear dry on the surface it may still be holding water inside.

How Much Does 1.5 Inch Thick Concrete Weigh Per Square Foot?

How much does 1.5 inches of concrete weigh per square foot? At a thickness of 1.5 inches, a concrete slab weighs about 18.75 lbs per square foot of surface area.

1.5 inches of concrete is a common thickness for walking stones.

How Much Does 4 Inch Thick Concrete Weigh Per Square Foot?

How much does 4 inches of concrete weigh per square foot? At a thickness of 4 inches, a concrete slab weighs about 50 lbs per square foot of surface area.

A 4 inch slab is the most common thickness used for sidewalks and walkways.

How Much Does 5 Inch Thick Concrete Weigh Per Square Foot?

How much does 5 inches of concrete weigh per square foot? At a thickness of 5 inches, a concrete slab weighs about 62.5 lbs per square foot of surface area.

5 inches of concrete is a common thickness for patios.

How Much Does 6 Inch Thick Concrete Weigh Per Square Foot?

How much does 6 inches of concrete weigh per square foot? At a thickness of 6 inches, a concrete slab weighs about 75 lbs per square foot of surface area.

6 inches of concrete is a common thickness for a driveway.

How Much Does 8 Inch Thick Concrete Weigh Per Square Foot?

How much does 8 inches of concrete weigh per square foot? At a thickness of 8 inches, a concrete slab weighs about 100 lbs per square foot of surface area.

8 inches of concrete is a common thickness for some spread footings and a patio’s edge footing.

How Much Does 10 Inch Thick Concrete Weigh Per Square Foot?

How much does 10 inches of concrete weigh per square foot? At a thickness of 10 inches, a concrete slab weighs about 125 lbs per square foot of surface area.

10 inches of concrete is a common thickness for some footings and a driveways edge footing.

How Much Does 12 Inch Thick Concrete Weigh Per Square Foot?

How much does 12 inches of concrete weigh per square foot? At a thickness of 12 inches, a concrete slab weighs about 150 lbs per square foot of surface area.

12 inches of concrete is a common thickness for footings.

Concrete Weight Per Cubic Foot

Another way to calculate concrete’s weight is by cubic foot. A cubic foot of concrete fills a space 1 foot wide x 1 foot long x 1 foot deep. This method is great for calculating the weight of concrete after it’s been demolished because there’s no slab to measure any more.

  • Concrete weighs 150 pounds per cubic foot.
  • Broken concrete weighs 75 pounds per cubic foot.
  • Finely smashed concrete weighs 100 – 150 pounds per cubic foot depending on how small the particles are.

It’s important to understand the real world difference between how much a solid concrete slab weighs per cubic foot and how much it weighs after its been demolished. The concrete itself weighs exactly the same before and after demolition. However, when you load broken concrete into a truck or dumpster there are lots of voids. The bigger the concrete chunks the more voids you’ll have. This means less weight per cubic foot.

Concrete’s weight is estimated in cubic feet when you have to transport it. This is because truck beds and dumpsters are measured by volume. For example an average size truck bed is 6.5′ long x 4′ wide x 2′ deep. That’s about 52 cubic feet worth of space. If you load it full of broken concrete that’s 3900 lbs. Too heavy for most full size pickups.

Understanding how much concrete weighs per cubic foot will come in handy whenever you have to load and transport demolished concrete.

Concrete Weight Per Cubic Yard

Another way to figure out the weight of concrete is by the cubic yard. A cubic yard of concrete fills a cube 3′ long x 3′ wide x 3′ deep.

Cubic yards are used to calculate large amounts of broken concrete.

  • A solid slab of concrete weighs 4,050 pounds per cubic yard.
  • A cubic yard of broken up concrete weighs 2,025 pounds.

How Much Concrete Can Fit In A Dumpster?

Most areas have a 10 tons (20,000 pounds) weight limit for dumpsters for safety reasons. Since one cubic yard of solid concrete weighs just over 4,000 pounds, its important to calculate the weight of a slab before calling for a dumpster.

We usually haul demolished concrete in 15 – 20 yard containers because they’re long, low and easy to fill. But you can’t fill them up all the way. A 20 yard dumpster filled with concrete would weigh over 25 tons which is way over the safe legal limit.

Most areas place a legal limit for how much weight a truck can safely carry. If you have a lot of concrete to get rid of, rent multiple dumpsters. First, use concrete’s weight per square foot or cubic foot to calculate the weight of your concrete. Then order concrete dumpsters with a 20,000 lb weight limit per dumpster in mind.

Summary: How Much Does Concrete Weigh Per Square Foot?

Concrete is a very dense and heavy building material. It’s made by mixing together cement, sand and stone with water. When dry concrete is mixed with water it becomes a semi-solid similar in consistency to thick oatmeal. It’s then poured into forms where it dries, hardens and grows strong. This process is called curing and takes around 28 days to complete. So how much does concrete weigh per square foot? Because concrete is thick you can’t determine it’s weight simply by measuring square feet. You also need to consider depth. A slab of concrete 1 inch thick weighs 12.5 lb per square foot. But a slab of concrete 4 inches thick weighs 50 lb per square foot. The thicker the concrete slab the more it weighs per square foot.

Measuring the square footage of a concrete slab is easy. Simply multiply its length x width (L x W). But to figure out concrete’s weight per square foot you also have to consider its depth. The calculation is length x width x depth (L x W x D).

Concrete slabs have volume which means you have to measure them in 3 dimensions. Square foot is a 2 dimensional measurement that only measures surface area. By adding depth to the equation you turn the measurement into cubic feet instead of square feet.

When calculating how much concrete weighs do the following:

  • Multiply the length x width of the slab to calculate its square footage.
  • Then multiply that number times the slab’s thickness.

Once you know a concrete slabs cubic feet, its easy to calculate its weight.

If you have any questions about concrete, email any time.

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