This chart shows how the size of concrete bag and the thickness of your 10’ x 10’ slab change the number of concrete bags you will need.
10’ x 10’ x 4” (1.23 cy)
10’ x 10’ x 5” (1.54 cy)
10’ x 10’ x 6” (1.85 cy)
How to do the Calculation Yards of Concrete Yourself
Bags per Cubic Yard of Concrete
40lb Bag covers 0.3 cubic feet, 27 cubic feet per cubic yard, 27/0.3 = 90 bags per yard
60lb Bag covers 0.45 cubic feet, 27 cubic feet per cubic yard, 27/0.45 = 60 bags per yard
80lb Bag covers 0.6 cubic feet, 27 cubic feet per cubic yard, 27/0.6 = 45 bags per yard
Yards of Concrete you’ll Need
Length x Width x Thickness = CF, CF / 27 = Cubic Yards Needed
10 x 10 x .33(4”) = 33 cubic feet, 33 / 27(cubic feet in a yard)= 1.23 cubic yards of concrete
10 x 10 x .42(5”) = 41.67 cubic feet, 41.67 / 27 = 1.54 cubic yards of concrete
10 x 10 x .5(6”) = 50 cubic feet, 50 / 27 = 1.85 cubic yards of concrete
Pouring a Slab with Bags of Concrete
Normally, bags of concrete are used for patch work, fence posts, and very small projects. Even though it is not as common, it is very possible to pour a 10 foot by 10 foot slab with bags of concrete.
Assuming you have read my post on how to frame a concrete slab, I will go into detail on how to pour with bags of concrete.
Your first step in pouring bags of concrete is, preparation.
The more prepared you are for pouring concrete, the easier it will be for all of us.
Considering you will be needing a minimum of 56 bags, you will doing a lot of mixing and will need to choose your method before you begin.
Ways to Mix Concrete
Some common ways to mix bags of concrete include; in a 5 gallon bucket with a mixing gun, in a wheelbarrow with a mixing gun or shovel, or in a cement mixer which can be rented at a construction rental store.
5 Gallon Bucket
When mixing anywhere from 56-167 bags, it may take too long to mix the concrete in a 5 gallon bucket and you may run out of time pouring the concrete. While the concrete mixed in the beginning will be curing before you are done mixing the later bags, leaving you with no time to finish your concrete slab.
With that being said, you can mix concrete in a 5 gallon bucket fairly easily. You will need a 5 gallon bucket, a water source, concrete mix, and a power mixer.
PRO TIP: Pour the water in the 5 gallon bucket first and then add the concrete mix on top of the water. This distinction will save you so much time and frustration when mixing concrete.
So, put about 3 inches of water in the 5 gallon bucket, then fill up the rest of the bucket with the concrete mix to about 3 inches below the rim of the bucket, then mix with power mixer.
If the mixture is too thick and too hard to mix, add splashes of water at a time to alter the consistency. You truly only need splashes at a time.
If the consistency is too wet, add more concrete mixture until you get the desired consistency you are looking for.
Use this alteration in the other 2 mixing options as well.
Wheelbarrow and Shovel
In a 5 gallon bucket you can mix less than one bag at a time, which can make this process lengthy.
Using the same process but in a wheelbarrow and using a power mixer or shovel to mix may help speed up the process.
You should be able to mix 5-10 bags at a time in a wheelbarrow and the mixed concrete is ready to be easily transported because it is already in a wheelbarrow to be moved.
If you do not have a power mixer and are using a shovel, this mixing option will be more labor intensive but it is 100% doable.
Most people do not have a cement mixer laying around their house, I mean I own a concrete company and I don’t have a cement mixer at my house.
Cement mixers are available to be rented at most construction supply shops and are very easy to use. The same process of mixing concrete in a bucket applies to a cement mixer just at a bigger scale.
Most cement mixers will produce 2-4 wheelbarrow’s worth of concrete. So if you are planning on pouring a larger slab with bags I would highly suggest renting a cement mixer and powering through a couple of wheelbarrow’s at a time.
CAUTION: The mixture you get with bags of concrete versus from a ready-mix company, produces a very different finishing surface. Ready-mix concrete is a much higher quality concrete which gives you a better surface for a cleaner finish.
Take this into consideration when finishing concrete produced from bags of concrete. I personally hate the look of finished bagged concrete but I also see things that the average person may not see in concrete. So if you like the look, all power to you!
The graph above is the answer you are looking for but I figured I would give you some assistance on how to mix the bags effectively.
Let me know in the comments below how your experience has been mixing concrete and which method you like using the most.