How do you calculate concrete yardage?

Ordering the right amount of concrete can be tricky. Moreover, it is a mix of math and caution. The success of your project depends on it. Get it wrong and you will be stuck with an expensive leftover mess. Even worse, running out on the material, just when the truck is about to leave. You need to make the right decisions every time. In this blog, we will discuss how to calculate the concrete yardage that is required for your dream project. With these tips you can order the right amount without making any mistakes. Moreover, you will be stress free when everything turns out to be perfect.

Understanding the Concrete Yardage Measurement

To start with, we should discuss the sale of concrete. The concerned authorities sell it in ton or square foot. Concrete is offered in cubic yards (CY). This is the standard industry that you must know.

•   What exactly is a cubic yard?
•   Think of it as a big cube.
•   The cube is 3 feet long, 3 feet wide, and 3 feet high.
•   When you multiply these dimensions, you will get 27 cubic feet.

Now divide that overall sum by 27 to come up with your final cubic yards. There are also many calculators of concrete available online. You can use them to check your math. The construction industry in the U.S. consumes about 500+ million cubic yards of concrete every year. The ordering has to be perfect or else it will be a waste of money

Step-by-Step Guide to Calculate Concrete Yardage

The majority of concrete jobs are a slab pour, either a patio, a driveway, or a basement floor. It is a simple rectangular figure and this simplifies the mathematics.

Step 1: Evaluate Your Dimensions

There are three measurements that you will require in your project:

•   Length (L): How long the area is.
•   Width (W): How wide the area is.
•   Thickness (T or Height (H): The amount of depth that the concrete will be poured.

The most important one is the fact that all three of these measures should be in the same measure. If the thickness is in inches, convert it to feet.  When both your length and breadth are in feet, keep them that way. Moreover, the inches have to be in feet while calculating the right amount. You can examine this example of a conversion for thickness:

An average sidewalk has a thickness of 4 inches. To bring this to the feet division, the inches are divided by 12 (there are 12 inches in a foot).

•   4 inches ÷ 12 = 0.333 ft
•   6 inches ÷ 12 = 0.5 ft

 

Therefore, when you are pouring a slab that is 4 inches thick, the number that you will put as the Thickness in the formula would be 0.333.

Step 2: Determine Volume (Cubic feet).

Since you have now measured everything in feet, the volume is easy to obtain. The volume of a shape of rectangular form is a simple formula:

•   Volume (Cubic Feet) = Length x Width x Thickness
•   Example: You are pouring a new patio, and the dimensions of the patio include: 20 feet long by 10 feet wide and 6 inches thick.
•   Switch height: 6 inches/12= 0.5 feet.
•   Cubic feet: 20 ftx10 ftx0.5 ft=100 cubic feet.

Step 3: Transform Cubic Feet into Concrete Yardage

This is the final step. You divide by the 27 magic numbers the total cubic feet you have just calculated.

•   Volume (Cubic Feet)/27=Cubic Yards.
•   Continue with: 100 cubic feet/27=3.70 cubic yards.
•   Therefore, 3.70 cubic yards of concrete would be required to fill a 20′ x 10′ x 6 type of patio.

Accounting for Irregular Shapes and Waste

The projects in the real world are not always rectangular. And you must have money to take into consideration the possibility of things going wrong. According to the National Ready Mixed Concrete Association, inappropriate estimating is one of the factors that lead to up to 3-5% of material wastage. Especially, when it comes to small residential pours which you can totally avoid with the help of a proper buffer.

How to Manage Odd Shaped Concrete Yardage Projects?

Anything that is not a simple rectangle will require you to subdivide the shape to smaller and simpler shapes.

•   L-shaped Patio: conceive it as two distinct rectangles. Divide the rectangle A in cubic yards. Division of rectangle B in cubic yards. Add the two numbers then.
•   Circular Patio: Area of the circle can be calculated by using the formula: A=pr.
•   In which r is the radius (half of the diameter).
•   Find the area in square feet.
•   Then, multiply the area by thickness (in feet) to obtain cubic feet.
•   Lastly, divide by twenty-seven to obtain cubic yards.

The Essential Waste Buffer

This is where human knowledge comes in. You always do not order the precise amount calculated. Why? The ground surface that the concrete is placed on (the subgrade) may not be completely even. It might have low spots.

•   The shapes that you make may not be exactly to size.
•   It never empties out and there is always some spillover or a bit of remaining in the truck.

The Rule of Thumb

•   You should always add 5 percent to 10 percent safety to your final cubic yards.
•   When you have calculated that you have 3.70 cubic yards, multiply it by 1.10 to get a 10 percent buffer.
•   3.70 CYx1.10=4.07 CY.

When ordering, you should round off to the nearest quarter or half yard. In this instance, you will be on the safe side to order 4.25 cubic yards. It is far less expensive to walk away with a little, instead of letting the truck leave with 0.25 cubic yards short.

What Influences the Price of Concrete Yardage?

You have to know the volume first. The other half is the cost which varies considerably. It was reported that the average ready-mix price in the first half of 2024 was approximately an average of 166.39 per cubic yard around the nation. But now the price is usually 150 to 180 or higher. Source: U.S. BLS Producer Price Index (PPI). The price is driven by a few important issues:

Project Volume (Short Loads): When the quantity ordered is less than the truckload (approximately 10 cubic yards), the supplier will impose a short-load fee. It will increase the cost of smaller orders by an amount of about 40-60 cubic yards.

Concrete Strength (PSI): Concrete is graded based on its compressive strength which is measured in pounds per square inch (PSI). 3, 000 PSI is the normal concrete strength in a patio and 4,000 PSI in driveways.

Additives and Mix Type: Special mixes such as fast setting, cold weather or high durability will add to the overall mix cost.

Delivery Distance: Suppliers also impose a surcharge per mile outside their local area, which is sometimes as much as $5-10 per mile.

Case Study: Understanding Concrete Yardage for a Small Patio

Take a 1 12- x 12- patio 4 inches thick poured by a homeowner. This is a common example of a DIY home project for you. You will understand how yardage is calculated:

•   Cubic Feet: 12 x12x (4/12) x ft=48 sneakers.
•   Calculated Yards: 48/27=1.78 CY
•   Add a buffer
•   Now round it off to 2 CY.

Usually, small projects like these are where the homeowners don’t calculate the right amount.  Without converting inches to feet and adding a buffer, your project will fail. The extra short load fees can increase the cost of the overall project as well.

FAQs

How many square feet does one cubic yard of concrete cover?

One cubic yard covers about 81 square feet, if your slab is 4 inches thick. If your slab is 6 inches thick, it will cover around 54 square feet.

Is it better to buy pre-mixed bags or get a truck delivery?

If your project needs more than one cubic yard it is better to get a truck delivery. It will save you some money.

What is the most common mistake when calculating concrete yardage?

The biggest mistake most people make is not to convert the thickness from inches to feet. This will lead to wrong calculation and you will order less amount that needed.