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Did you know that China makes up 60% of the world's concrete production? In 3 years they used more concrete than the United States did in the entire 20th Century.

They required exact calculations for the amount of concrete to use in their projects. You may not need as much, but it's just as vital you buy the correct amount.

Using a concrete calculator ensures you get it right, whether it's premixed concrete or concrete by the bag. This can save you headaches and a potentially ruined project.

Below we take a closer look at what concrete is and how it works. And if you like using our site, please share it with your friends!


Why use a concrete calculator?

Our concrete calculator shows you the cubic area of your project, the amount of premixed concrete you'll need, and how many concrete bags that translates to. It's a helpful tool that simplifies a multi-step process with extreme accuracy.

It's essential to lay the entire project in one go. If you try to lay more after the first batch starts curing they won't combine and you will end up with two pieces of concrete.

This can happen if you make even the smallest error on your estimations. Using a concrete calculator can help you avoid that.

Even if you've already done the math, it's a good idea to verify your numbers with a concrete calculator. Because we're human and sometimes make mistakes, this tool adds an extra 10% for spillage.

What is concrete?

It's easy to confuse concrete with cement, but they are not the same thing. Cement is an ingredient of concrete.


Concrete has three basic ingredients, water, aggregate, and Portland Cement. Aggregate can be rock, sand, or even gravel. The cement is a powder that binds the water and aggregate together.


When these three ingredients mix together, the cement and water combine. This combination creates a paste that coats the aggregate.

The water creates a chemical reaction which makes the concrete workable. Once the mixture cures it becomes a hard substance.

The amount of water you add dictates how strong the finished product will be. The lower your water to cement ratio, the stronger your concrete will be.

Special Types

Pervious concrete does not have fine particles. Once poured, it is about 15-25% air pockets.

This concrete lets water flow through it to the soil underneath. It works well in climates that freeze and thaw a lot.

Nanoconcrete uses a high energy mixing process. This concrete works well when pouring the concrete into a form with fine details.

Microbial concrete has bacteria that increases the compression strength.

Polymer concrete has additives to increase tensile strength and make it water impervious.

How can concrete be purchased?

You have three options for how you buy concrete. You can buy bags, a ready mix in a spin tank, or a cement truck.

Once you know how much concrete you need, pick the supply option that fits the size of the project.

Small Projects

Concrete bags are best for small projects. You can buy 50, 60, 80, or 90 pound bags.

Mid Sized Projects

A ready mix in a spin tank is best. This will let you get an even pour over the entire project.

Large Projects

Ordering ready mix in a cement truck is the way to go. The contractor will specially mix your contract for your project.

How much does 1 bag of concrete cover?

You will find concrete sold in 50, 60, 80, and 90-pound bags. Most residential projects are 4 or 6 inches thick.

A 50-pound bag will cover:

  • 1 square foot that is 4 inches thick
  • 0.71 square feet if you make the slab 6 inches thick
  • A 60-pound bag will cover:

  • 1.25-foot square that is 4 inches deep
  • 0.834 square feet for a six-inch deep square
  • An 80-pound bag will cover:

  • 1.67 square feet that is 4 inches deep
  • 1-foot square if the slab is 6 inches deep
  • A 90-pound bag covers:

  • 1.67 square feet that is 4 inches deep
  • 1.25 square feet if the slab is 6 inches deep

  • How is it applied?

    You should lay concrete as close to its final location as possible. Handling and moving concrete can cause it to break.

    Step One: Laying

    Have your concrete poured directly from the truck to the slab location. For smaller projects mix your concrete at the site where you plan to use it.

    It's best to use a short handled square shovel to spread the concrete around. A rounded shovel will not give you an even smooth surface.

    Do not pour large piles and then try to spread it out. Start at one edge and work your way across the site.

    Step Two: Finishing

    Depending on your project you need to give the surface of your concrete a finish. For surfaces that need grip like steps, broom them. This will give the concrete a rough texture.

    For surfaces that need a smooth finish, scrape or strike-off them. This cuts off the excess concrete by moving a straight edge over the entire surface.

    Large concrete projects need jointing. This prevents ugly cracks from forming.

    You can insert wood or plastic strips to make joints in the concrete. You can also make sawcut joints after the concrete has hardened.

    If you are jointing the concrete, you need to float the surface after you place the strips. This gives you a clean exterior by embedding any aggregate just below the surface.

    Step Three: Curing

    Concrete will take about a week to cure before it is usable. During this time you need to prevent it from getting too hot, cold, or damp.

    If you don't cure the finished concrete it will have spider cracking. The surface will also dust off during use.

    How do you calculate how much concrete you need?

    To calculate how much concrete you need, we recommend using a concrete calculator. But it's also helpful to know how to figure it out by hand, too.

    Step One: Calculate Area

    Start by multiplying the length by the width of the area in feet. This will give you the flat square footage.

    Step Two: Determine Volume

    Then multiply this number by the depth in feet. This will give you the entire volume.

    Step Three: Convert To Yards

    You will order your concrete in yards. So divide your number by 27. This is the number of cubic feet in a yard.

    Step Four: Add Spillage

    If you have ever laid tile or laminate flooring you have heard of waste. The same concept applies to concrete.

    You should add 10% to your calculation for spillage. This covers any spills or variations in your slab depth.

    Alternatively, using a concrete calculator can make things a heck of a lot easier. Plus, you're off to a great start by having this guide in your arsenal.

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