When starting any new project, it’s a good idea to know how much raw material you’ll need upfront so you can estimate costs and reduce the number of trips back to your local home improvement store! We’ve added this Cement Calculator tool to help with estimating how much concrete you’ll need for your next project.
Cement versus Concrete
When estimating the amount of material you’ll need, it’s important to understand the difference between cement and concrete. Cement is a binding agent which means it holds other substances together. It’s what you could consider the active ingredient in concrete. In the simplest example, when you combine cement, sand, gravel, and water, you get concrete which is the material you generally work with to create slabs, posts, footers, and other structures. If you’re not planning on mixing your own concrete by combining cement, aggregates (gravel and sand), and water, use the tool below to estimate the amount of concrete you’ll need. That will tell you the number of cubic yards if you’re having it delivered or it will give you the number of bags of premixed concrete to purchase.
The Cement Calculator
If you’re planning to mix the concrete yourself, still use the tool to figure out how many cubic yards you’ll need, but then skip to the last section and we’ll tell you how to convert the number of cubic yards into the amount of raw materials.
How to mix your own concrete
If you don’t want to buy premixed concrete you can mix your own and save money in the process. To make basic concrete, mix 1 part Portland cement, 1.5 parts large-aggregate such as gravel, 1 part small-aggregate such as sand, and .5 parts water.
To show how this is used, we’ll calculate the ingredients necessary to create a 4.5″ thick 6′x6′ slab. Using the calculator above, we can see that this slab will require 0.5 cubic yards of concrete.
So to calculate the ingredients, follow these steps:
- Use the tool above to calculate the total cubic yards of concrete needed.
- To find out how much cement is needed, divide the total cubic yards by 4 and then multiple by 27. This will give you the number of cubic feet of cement needed for the project. In our example, 0.5/4*27 = about 3.4 cubic feet of cement. This, conveniently, is also the amount of sand you’ll need since sand and cement are equal parts.
- To find out how much gravel is needed, multiple the amount of cement needed by 1.5. In our example, we would need 3.4*1.5 = about 5 cubic feet of gravel.
- To find out how much water is needed, multiple the amount of cement needed by 0.5. In our example, we would need 3.4*0.5 = 1.7 cubic feet of water. You can multiple this by 7.5 to get the number of gallons needed. 1.7 * 7.5 = 12.75 gallons.