Concrete is a valuable material in any construction project and it’s important to get the right amount for every job.
Whether you’re pouring a new driveway or laying a pool foundation, the accuracy of your cement calculations can mean the difference between success and failure.
Before we proceed with the calculations, it’s important that one is aware of how direct estimation works.
Once you have a feel for the material and its properties, it’ll be much easier to ballpark an estimate for your project. With that being said, let’s begin!
Formula To Find Out the Volume Of Concrete
Finding the volume of concrete is crucial to ensure that you get the right amount for your project. This means that understanding the volume will let you know how much concrete you’ll need for the project. The formula to calculate the volume of concrete is simple and straightforward:
V = L x W x D
Where V is the volume, L is the length, W is the width and D is the depth. Just enter all of these values into our calculator to determine how much concrete you will need.
For example, the box or area you’re working on has a 1-meter length, 2 meters height, and 1-meter depth, then:
Volume = 1 * 2 * 1 = 2 cubic meters.
Hence, for filling the one cubic meter of the box, you need 25 KN of concrete where 1 KN = 100 kgs)
So, for filling two cubic meters, you need a 2 * 25 = 50 KN mixture of cement. This means the volume or amount of concrete is the evaluation of a 3D object.
The formula varies according to the shape. But the method remains the same for calculating the volume of any of the figures. It is the multiplication of three dimensions.
For instance, take the cylinder that neither has length nor breadth. For calculating the cylinder, you need to multiply the area of a circle by the height of the cylinder. It is then:
The volume of cylinder = Depth/height * Surface Area
Once you have the volume, what are the next steps to find out the amount of cement needed?
Simple Steps That Every Concrete Calculator Use
Below are simple and easy steps to evaluate the amount of cement mixture for any shape:
- Check out or decide on the desired thickness.
- Measure the width and length of the space that you want to cover.
- Evaluate the product of length and width for identifying the square foot.
- Now convert the thickness from inches to feet.
- Calculate the product of thickness (in feet) and square feet for cubic feet result.
- Then convert cubic feet to cubic yards by multiplying with 0.037.
For determining the number of concrete bags you need, divide the overall cubic yards by yield. You can utilize the following yields according to the size of one bag:
- 40 pounds bag yield has 0.011 cubic yards
- A 60-pound bag can cover 0.017 cubic yards
- The 80-pound bag can yield 0.022 cubic yards
Calculate the Amount For Footings
The footing is the base for a structure. This disperses the weight over the wide area. This is helpful for preventing soil shifting and settling issues. Spot footings and continuous spread footings are two of the most commonly used structural foundations.
Spot footings are used when the weight of a structure is relatively low, and it requires support from only one side. On the other hand, continuous spread footing helps in distributing loads over more than one point evenly.
Before you calculate the amount of concrete needed, you’ll need to first determine which kind of footing will be used. From there, you can then use the formula below:
Concrete Calculation Formula For Spot Footing
Here are the steps required to calculate the amount of concrete for spot footing:
Step 1
Spot footing is usually about 2 by 2 square feet, which is around 10 to 12″ deep. It means the length is 2′, width is 2′, and height/depth is 12″.
Step 2
So, you have to convert all measurements into feet by dividing the depth/height by 12″.
12″/12″ =1 foot
Step 3
From there, you have to multiply all dimensions for evaluating the cubic feet of cement mixture you require.
Volume = L * W * H/D = 2′ * 2′ * 1′ = 4 cubic feet
Step 4
Find out the product of the number of posts you need to support with spot footing. For instance, a pier supports eight posts 4′ * 8 = 32 cubic feet.
Step 5
Concrete is available in cubic yards. However, our calculated measurement is in cubic feet, so you need to convert it into cubic yards. Multiply your cubic feet result by 0.037037037.
32 cubic feet * 0.37037=1.185185 184 cubic yards.
With that being said, the cement required for this type of footing ranges between 3000 and 5000 PSI in compression.
Concrete Calculation For Continuous Spread Footing
The
Step 1
Continuous spread footing is generally about 16 inches to 24 inches wide with a depth of about 6 inches to 16 inches deep. So building dimensions are 24′ by 32′, which means we need to find out the perimeter for the length. Length is 24′ + 32′ + 24′ + 32 = 112′; width = 24′ and depth = 16′.
Step 2
Now convert all measurements into feet the same as above by dividing the width and depth by 12″.
24″/12″ = 2 feet and 16″/12″ = 1.33 feet
Step 3
Multiply all dimensions for determining the cubic feet you require. 112′ * 2′ * 1.33′ = 297.92 cubic feet.
Step 4
As we already know, concrete is available in cubic yards, so let us convert cubic feet into cubic yards by multiplying it by 0.37037037.
297.92 cubic feet * 0.37037037 = 11.03407406 cubic yards. Cement in this type of footing ranges from 2000 to 5000 PSI in compression.
Grade Beam Footing Evaluation
The third and less frequently advantageous footing is the grade beam footing which is usually the sum of continuous spread footing and spot footing.
To calculate grade beam footing, evaluate continuous spread footing first followed by spot footing, and add cubic yards altogether to determine the amount needed for this sort of footing.
Calculation Of Cement For Column
There is an online concrete calculator for columns, footing, walls, etc., that can be helpful for you to find out the volume and weight of the concrete you require for your project. However, you need to follow a few steps before that, and you can also calculate it manually like:
Columns are of any shape, such as rectangular or circular. But remember,
Volume = surface area * depth
Rectangle Column Shape
Let’s say your rectangular column has length = 0.6m, breadth = 0.4m, and height of 3m. For calculating the top surface area and to get the product of it with depth/height:
Volume Required For Rectangular column = 0.6 * 0.4 * 3= 0.72 cubic meter
Circular Column Shape
Suppose the circle’s radius is 0.25 m, then the volume of the circle column is the product of the surface area of the circle and the height of the column.
Volume of circle column = Pie * (square of radius) *3 = 3.14 * 0.25 * 0.25 * 3 = 0.58 cubic meter.
Concrete Evaluation For Slabs
The slab is available in the shape of a rectangle. So for evaluating the volume needed for the slab, please find out the surface area and multiply it by the thickness/depth of the slab. Suppose the rectangles measurements are:
Length = 6 m; breath = 5m; depth/thickness = 0.15m
Volume = Area of rectangular slab * depth/height
Step 1
Evaluate the area of the rectangle with its measurements (length and width) –
Area = length * width = 6 * 5 = 30 square meter
Step 2
Find out The volume of the concrete. V = LBH
Volume of concrete needed = 30 square meter * 0.15 = 4.5 cubic meter
Step 3
Convert 4.5 cubic meters into cubic yards. One cubic meter = 1.30795 cubic yards. So,
4.5 cubic meters * 1.30795 = 5.88578 cubic yards.
Concrete For Wall Calculation
For the wall made up of concrete, the calculation is almost the same – height * length * width. Suppose the volume in cubic meters for the wall has a height of 2m, width of 20 cm, and length of about 4m.
Volume of concrete needed = 2 * 4 * 0.2= 1.6 cubic meters. You will then convert it into cubic yards, and you will get the concrete amount you need for a wall.
Concrete Calculations For Curb, Staircase, and Gutter
More complex forms like a gutter, staircase and curb utilize the same approach, but the calculation is complicated. So you need a calculator for it. For the gutter and curb, it is the situation to combine the volume of the curb and gutter using the below formula:
Curb depth * (height of curb + thickness of flag) * length + width of gutter * thickness of flag *length
The staircase is the most complex one because we need to account for the rising volume of concrete for every subsequent stair.
We need to evaluate volume for n number of steps. Suppose n = step 2 having a raise of 6 inches, length of 6 inches, and width of 4 feet, convert inches into feet. Six inches will be 0.5 feet. So, calculation will be n*l*w*h = 2 * 0.5 * 0.5 * 4 = 2 cubic feet. Convert it into cubic yards.
Final Words
For the construction project, the concrete calculation is a necessary step to get the right amount of required material.
To calculate grade beam footing, columns, slabs, and walls you need to follow certain steps provided in this article and use the online calculator for more complicated forms like curbs, stairs, and gutters.
This guide should help you estimate the volume of concrete needed for your project. But make sure to account for any additional material necessary (like reinforcement), so you don’t end up with too little or too much concrete.
A good rule of thumb is to get about 10-20% more than the calculated volume to ensure you have enough for the job.
