A yard of concrete is the same as 27 cubic feet of concrete. This measurement, known as a cubic yard, is a standard way to measure concrete volume, especially when ordering ready mix concrete for building projects.
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What is a Cubic Yard?
Think of a yard as a measure of length, like three feet. A cubic yard is a measure of volume. It is like a box. This box is one yard long, one yard wide, and one yard high. Since one yard is three feet, this box is three feet long, three feet wide, and three feet high.
To find the volume of this box, you multiply length by width by height.
3 feet * 3 feet * 3 feet = 27 cubic feet.
So, one cubic yard takes up the same space as 27 cubic feet. This is the main idea when talking about concrete quantity.
Why Knowing the Cubic Yard Volume Matters
Knowing how many cubic feet are in a yard is very important for many reasons. It helps you figure out how much concrete you need for your project. This is part of estimating concrete costs and needs. If you order too little, your project stops. If you order too much, you waste money. Ready mix concrete companies sell concrete by the cubic yard. So, you must know your project’s volume in cubic yards to order correctly. This is about getting the right amount of concrete needed.
Deciphering Concrete Volume Calculation
Figuring out the right concrete quantity needs a few simple steps. You need to measure the area where the concrete will go. Then you need to measure the depth or thickness. These steps help you find the cubic yard volume you need. This is a key part of concrete volume calculation.
Measuring Your Project Space
First, you need to know the shape of your project area. Most concrete projects are squares, rectangles, or circles.
For Square or Rectangle Areas
- Measure the length of the area in feet.
- Measure the width of the area in feet.
- Measure the depth (thickness) of the concrete you want in inches.
Write these numbers down carefully.
For Circle Areas
- Find the center of the circle.
- Measure the distance from the center to the edge. This is the radius, measure it in feet.
- Measure the depth (thickness) of the concrete you want in inches.
Write these numbers down too.
For Odd Shapes
Odd shapes can be harder. You might need to break the shape into smaller squares, rectangles, or circles. Figure out the volume for each small piece. Then add the volumes together.
Fathoming the Calculation Steps
Once you have your measurements, you can figure out the total volume needed in cubic feet.
Step 1: Get All Measurements in Feet
You measured length and width in feet. But you measured depth in inches. You need to change the depth measurement from inches to feet. There are 12 inches in one foot.
To change inches to feet, divide the inches by 12.
- Example: If your depth is 4 inches, divide 4 by 12.
4 inches / 12 inches/foot = 0.333 feet (we often use 0.33 or 0.34 feet for 4 inches). - Example: If your depth is 6 inches, divide 6 by 12.
6 inches / 12 inches/foot = 0.5 feet.
It is important to be careful with this step. The depth makes a big difference in the total amount of concrete needed.
Step 2: Calculate Volume in Cubic Feet
Now that all measurements are in feet, you can find the volume in cubic feet.
For Square or Rectangle Areas
Multiply length by width by depth (in feet).
- Volume (cubic feet) = Length (feet) * Width (feet) * Depth (feet)
Example: A patio is 10 feet long and 10 feet wide. You want the concrete to be 4 inches thick.
* Length = 10 feet
* Width = 10 feet
* Depth = 4 inches. Change to feet: 4 / 12 = 0.333 feet.
* Volume = 10 feet * 10 feet * 0.333 feet = 33.3 cubic feet.
For Circle Areas
The area of a circle is found using the formula Pi (π) times the radius squared (r * r). Use 3.14 for Pi. Then multiply the area by the depth (in feet).
- Volume (cubic feet) = π * radius (feet) * radius (feet) * Depth (feet)
Example: A round hot tub base has a radius of 4 feet. You want the concrete to be 6 inches thick.
* Radius = 4 feet
* Depth = 6 inches. Change to feet: 6 / 12 = 0.5 feet.
* Volume = 3.14 * 4 feet * 4 feet * 0.5 feet
* Volume = 3.14 * 16 * 0.5 cubic feet
* Volume = 25.12 cubic feet.
Grasping the Volume Conversion: Feet to Yards
You found the volume in cubic feet. But ready mix concrete is sold by the cubic yard. You need to change cubic feet to cubic yards.
Remember, one cubic yard is 27 cubic feet.
To change cubic feet to cubic yards, divide the total cubic feet by 27.
- Volume (cubic yards) = Volume (cubic feet) / 27
Example using the patio calculation (33.3 cubic feet):
* Volume (cubic yards) = 33.3 cubic feet / 27 cubic feet/cubic yard
* Volume (cubic yards) = 1.23 cubic yards.
Example using the circle calculation (25.12 cubic feet):
* Volume (cubic yards) = 25.12 cubic feet / 27 cubic feet/cubic yard
* Volume (cubic yards) = 0.93 cubic yards.
This volume conversion is a very important step when ordering concrete. It gives you the concrete yard measurement you need for your order.
Common Project Examples and Calculations
Let’s look at a few common home projects and figure out how much concrete you might need. This helps with estimating concrete quantity.
Example 1: A Simple Sidewalk
Imagine you want to pour a sidewalk. It will be 50 feet long and 3 feet wide. You want it 4 inches thick.
- Measurements:
- Length = 50 feet
- Width = 3 feet
- Depth = 4 inches
- Change Depth to Feet:
- 4 inches / 12 inches/foot = 0.333 feet
- Calculate Volume in Cubic Feet:
- Volume = 50 feet * 3 feet * 0.333 feet
- Volume = 150 * 0.333 cubic feet
- Volume = 49.95 cubic feet (Let’s say 50 cubic feet)
- Change Cubic Feet to Cubic Yards:
- Volume = 50 cubic feet / 27 cubic feet/cubic yard
- Volume = 1.85 cubic yards.
So, you would need about 1.85 cubic yards of concrete for this sidewalk. When ordering ready mix concrete, they usually sell in half-yard or quarter-yard amounts. You would likely order 2 cubic yards to be safe.
Example 2: A Garage Slab
Let’s figure out concrete for a garage floor. The garage is 20 feet by 24 feet. The concrete will be 4 inches thick.
- Measurements:
- Length = 24 feet
- Width = 20 feet
- Depth = 4 inches
- Change Depth to Feet:
- 4 inches / 12 inches/foot = 0.333 feet
- Calculate Volume in Cubic Feet:
- Volume = 24 feet * 20 feet * 0.333 feet
- Volume = 480 * 0.333 cubic feet
- Volume = 159.84 cubic feet (Let’s say 160 cubic feet)
- Change Cubic Feet to Cubic Yards:
- Volume = 160 cubic feet / 27 cubic feet/cubic yard
- Volume = 5.93 cubic yards.
For this garage slab, you would need almost 6 cubic yards of concrete. Ordering concrete would likely be 6 cubic yards.
Example 3: Footings for a Wall
Maybe you are pouring footings. These are long, narrow concrete bases. Let’s say the footing is 60 feet long. It is 16 inches wide and 8 inches deep.
- Measurements:
- Length = 60 feet
- Width = 16 inches
- Depth = 8 inches
- Change Width and Depth to Feet:
- Width = 16 inches / 12 inches/foot = 1.333 feet
- Depth = 8 inches / 12 inches/foot = 0.667 feet
- Calculate Volume in Cubic Feet:
- Volume = 60 feet * 1.333 feet * 0.667 feet
- Volume = 60 * 0.889 cubic feet
- Volume = 53.34 cubic feet
- Change Cubic Feet to Cubic Yards:
- Volume = 53.34 cubic feet / 27 cubic feet/cubic yard
- Volume = 1.98 cubic yards.
You would need about 2 cubic yards for these footings.
These examples show the concrete volume calculation steps. They help you estimate concrete needed for different jobs. Getting the concrete quantity right saves time and money.
Factors Affecting Amount of Concrete Needed
Your calculation gives you a base number. But you should often add a little extra. Why? Because things happen on a job site. This extra amount is for safety. It helps ensure you have enough concrete. It is part of smart estimating concrete.
Here are reasons you might need more concrete than your base calculation:
- Uneven Ground: The ground you pour on is rarely perfectly flat. You might dig deeper in some spots. This uses more concrete.
- Over-Excavation: You might dig out more dirt than you planned. This makes the hole bigger. A bigger hole needs more concrete.
- Forms Not Perfect: The wood or metal forms you use to hold the concrete might not be set up perfectly tight or straight. This can let concrete spread out a little more.
- Waste: Some concrete might be spilled. Some might stay in the truck chute. Some might be left in the wheelbarrow. Small amounts of waste add up.
- Settling: Concrete can settle a bit as it is poured and worked.
- Changes: Sometimes plans change a little during the project.
Because of these things, it is wise to add 5% to 10% extra to your calculated concrete quantity.
Let’s go back to the patio example. We needed 1.23 cubic yards.
If we add 10% for safety:
* Extra amount = 1.23 cubic yards * 0.10 = 0.123 cubic yards
* Total needed = 1.23 cubic yards + 0.123 cubic yards = 1.353 cubic yards.
When ordering concrete, you would likely round this up to the next available amount, maybe 1.5 cubic yards. Ordering concrete with a little extra is usually better than ordering too little. Running short means paying for a second, small delivery. This second trip costs a lot more per yard.
Using a Concrete Calculator
Doing the math each time is okay. But a concrete calculator makes it easy. Many websites and apps offer free concrete calculators.
How they work:
1. You enter the shape of your project (square/rectangle, circle, etc.).
2. You enter your measurements (length, width, depth). Make sure to pick the right units (feet, inches, yards).
3. The calculator does the concrete volume calculation for you.
4. It gives you the concrete quantity needed, usually in cubic feet and cubic yards.
Using a concrete calculator helps avoid math mistakes. It is a quick way to get the cubic yard volume for ordering concrete. It is a very helpful tool for estimating concrete needs.
Ready Mix Concrete and Ordering
Ready mix concrete is mixed at a plant and delivered to your job site in a truck. It is the most common way people get concrete for larger projects. Ready mix is sold by the cubic yard.
When you call a ready mix company to place an order for concrete, they will ask you:
- The total concrete quantity in cubic yards. (This is where your calculation or calculator result comes in).
- The mix design needed (strength, additives, etc. – this depends on your project, check your building plans or ask your contractor).
- The date and time you need delivery.
- Your project address.
- Information about access for the truck (can a heavy truck get close to where you need the concrete?).
Giving them the correct cubic yard volume is key. They use this concrete yard measurement to mix the right amount.
Minimum Order Amounts
Ready mix companies often have a minimum order size. This is often 1 or 2 cubic yards. For very small jobs needing less than the minimum, ready mix might not be cost-effective. You might need to mix concrete yourself from bags.
Planning for Delivery
Think about how you will get the concrete from the truck to your project. This might be with:
* A chute from the back of the truck (if the truck can get right next to the spot).
* Wheelbarrows (for shorter distances, but hard work).
* A concrete pump (for longer distances or hard-to-reach spots, costs extra).
Plan this before the truck arrives.
Getting Concrete from Bags
For small jobs, like setting fence posts or a small repair, mixing concrete from bags is easier and cheaper than a ready mix truck. Concrete bags are sold by weight, like 60 lbs or 80 lbs. They tell you on the bag how much concrete volume they make when mixed. This is usually in cubic feet.
Example: An 80 lb bag of concrete mix might make about 0.6 cubic feet of concrete.
If your small project needs 5 cubic feet, you would divide:
5 cubic feet / 0.6 cubic feet/bag = 8.33 bags.
You would buy 9 bags.
You can see that mixing from bags gives you the volume in cubic feet. If you needed to know that in cubic yards, you would divide by 27.
8.33 bags makes 5 cubic feet.
5 cubic feet / 27 cubic feet/cubic yard = 0.185 cubic yards.
Mixing bags is good for small amount of concrete needed, where the cubic yard volume is small.
Tables for Quick Reference
Here are some tables to help you see volume conversion and typical depths.
Cubic Feet to Cubic Yards Conversion
| Cubic Feet (cu ft) | Cubic Yards (cu yd) |
|---|---|
| 1 | 0.037 |
| 5 | 0.185 |
| 10 | 0.37 |
| 15 | 0.556 |
| 20 | 0.74 |
| 27 | 1 |
| 30 | 1.11 |
| 40 | 1.48 |
| 50 | 1.85 |
| 100 | 3.7 |
| 200 | 7.41 |
| 500 | 18.52 |
This table helps you quickly see the volume conversion. Remember that 27 cubic feet is 1 cubic yard volume.
Common Depths in Feet
It helps to know the depth in feet for common concrete thicknesses.
| Depth in Inches | Depth in Feet (approx.) |
|---|---|
| 2 | 0.17 |
| 3 | 0.25 |
| 3.5 | 0.29 |
| 4 | 0.33 |
| 5 | 0.42 |
| 6 | 0.50 |
| 8 | 0.67 |
| 10 | 0.83 |
| 12 | 1.00 |
Use this table when doing your concrete volume calculation. Change your depth measurement to feet before finding cubic feet.
Cubic Yards Needed for Common Areas (at 4 inch depth)
Let’s see how much concrete for some common sizes at a typical 4 inch depth. (Depth is 0.333 ft).
| Area (Length x Width in Feet) | Volume in Cubic Feet (Area * 0.333 ft) | Volume in Cubic Yards (cu ft / 27) |
|---|---|---|
| 5 ft x 5 ft (25 sq ft) | 25 * 0.333 = 8.33 cu ft | 8.33 / 27 = 0.31 cu yd |
| 10 ft x 10 ft (100 sq ft) | 100 * 0.333 = 33.3 cu ft | 33.3 / 27 = 1.23 cu yd |
| 12 ft x 12 ft (144 sq ft) | 144 * 0.333 = 48 cu ft | 48 / 27 = 1.78 cu yd |
| 15 ft x 15 ft (225 sq ft) | 225 * 0.333 = 75 cu ft | 75 / 27 = 2.78 cu yd |
| 20 ft x 20 ft (400 sq ft) | 400 * 0.333 = 133.2 cu ft | 133.2 / 27 = 4.93 cu yd |
| 24 ft x 24 ft (576 sq ft) | 576 * 0.333 = 192 cu ft | 192 / 27 = 7.11 cu yd |
| 50 ft x 3 ft (150 sq ft) | 150 * 0.333 = 50 cu ft | 50 / 27 = 1.85 cu yd |
This table helps you quickly estimate concrete needs for common sizes. Remember to add a bit extra for safety.
Planning Your Concrete Project
Good planning is very important. Knowing the amount of concrete needed is just one part. Here are other things to think about:
- Weather: Do not pour concrete in very hot, cold, or rainy weather. Check the forecast.
- Tools: Have all your tools ready before the concrete arrives. You will need shovels, rakes, screeds (a straight board to level the concrete), floats (tools to smooth the surface), and safety gear (gloves, glasses, boots).
- Forms: Make sure your forms are strong and properly set up. They hold the concrete in place.
- Subgrade: The ground under the concrete (subgrade) must be ready. It should be level, compacted, and maybe have gravel.
- Helpers: Get enough people to help. Concrete work is hard and fast. You need people to move, spread, and finish the concrete quickly.
- Curing: After pouring, concrete needs to cure. This means keeping it moist so it gets strong. You might cover it with plastic or use a curing compound.
Thinking about all these things helps your project go smoothly.
Reviewing the Cubic Yard Measurement
Let’s go over the main idea again.
- A cubic yard is a measure of volume.
- It is a cube that is 1 yard (3 feet) on each side.
- The volume is 3 ft * 3 ft * 3 ft = 27 cubic feet.
- So, 1 cubic yard = 27 cubic feet.
This cubic yard volume is the standard concrete yard measurement used for ordering ready mix concrete. Knowing how to change cubic feet to cubic yards (divide by 27) is key for figuring out the amount of concrete needed for your project.
Whether you use a pencil and paper for concrete volume calculation or a concrete calculator, getting this number right is vital for good estimating concrete and a successful project.
Frequently Asked Questions (FAQ)
Here are some common questions people ask about concrete amounts.
Q: How much does one cubic yard of concrete weigh?
A: The weight can change a little based on the mix, but a standard cubic yard of concrete weighs about 3,700 to 4,000 pounds. That is about 1.85 to 2 tons. This is why a ready mix truck is very heavy!
Q: Can I mix a cubic yard of concrete myself from bags?
A: In theory, yes. You would need about 45 bags of 80 lb concrete mix (since each makes about 0.6 cu ft, and 45 * 0.6 = 27 cu ft). But mixing this much by hand or with a small mixer is a huge job. It is very hard work and takes a lot of time. For a cubic yard or more, ordering ready mix concrete is almost always better.
Q: How thick should my concrete slab be?
A: This depends on what the concrete will be used for.
* Sidewalks and patios: Usually 4 inches thick.
* Driveways: Usually 4 to 6 inches thick, depending on the vehicles using it.
* Garage floors: Usually 4 inches thick for cars, maybe 6 inches for heavier use.
* Heavy equipment areas or structural slabs: Can be 6 inches or much thicker.
Always check local building codes or project plans for the right thickness. This thickness is your “depth” for concrete volume calculation.
Q: What is the smallest amount of ready mix concrete I can order?
A: This varies by company. Many have a minimum order of 1 cubic yard or 2 cubic yards. If you need less than the minimum, they might still deliver, but they will charge you the minimum price.
Q: Why do I need to add extra concrete to my order?
A: You add extra (often 5% to 10%) to cover things like uneven ground, forms that bulge a little, small spills, and to make sure you do not run short. Running short means waiting for a second delivery, which costs more time and money. It is better to have a little too much than not enough. This extra is factored into good estimating concrete.
Q: Does the type of concrete mix change the volume?
A: No, the type of mix (like strength or additives) does not change the volume it takes up. One cubic yard is still 27 cubic feet, no matter the mix type.
Q: What is the difference between concrete, cement, and mortar?
A: People often mix these words up.
* Cement is a powder, like glue. It is an ingredient.
* Concrete is a mix of cement, sand, gravel (or crushed stone), and water. It is a strong building material used for slabs, foundations, etc.
* Mortar is a mix of cement, sand, and water. It is used to hold bricks or blocks together. It does not have the large gravel found in concrete.
This guide should help you feel more ready to figure out how much concrete you need. Remember the main idea: a yard of concrete means one cubic yard, which is 27 cubic feet. Use your measurements, do the simple math or use a concrete calculator, add a little extra, and you will be ready for ordering concrete. Getting the concrete quantity right is a big step toward a successful project.