Trying to figure out how much concrete you need for a project can feel tricky. A common question is: how many bags of concrete make one cubic yard? The simple answer is that it depends on the size of the concrete bag you are using. For a standard 80-pound bag, you generally need about 45 bags to get one cubic yard of concrete. If you are using standard 60-pound bags, you will need about 60 bags to make one cubic yard. This calculation helps you figure out how much concrete you need per bag and how many concrete bags per yard are necessary for your job.
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Interpreting Concrete Bag Volume
When you buy concrete at the store, it comes in bags. These bags have dry mix inside. You add water to this mix to make wet concrete. The bags are usually sold by weight. Common sizes are 40 pounds, 50 pounds, 60 pounds, and 80 pounds. But the weight isn’t what tells you how much space the wet concrete will fill. What matters is the volume of wet concrete each bag makes. This is often called the concrete yield per bag.
Each bag tells you how much wet concrete it will make. This volume is usually given in cubic feet (cu ft). Why cubic feet? Because a cubic yard is a big amount, and bags are smaller. Many bags are measured in cubic feet for easier use on smaller jobs. Knowing the concrete bag size volume is the first step to figuring out how many bags equal a cubic yard.
Grasping Cubic Yards
What exactly is a cubic yard? Think of a box. This box is 3 feet long, 3 feet wide, and 3 feet tall. The space inside that box is one cubic yard. It’s a measure of volume, like gallons for milk or liters for soda, but for bigger amounts of stuff like dirt, gravel, or concrete.
A cubic yard is a lot of material. To help picture it, think about:
- A standard washing machine is roughly one cubic yard.
- A large refrigerator is close to one cubic yard.
- A typical pickup truck bed can hold about half a cubic yard.
So, pouring one cubic yard of concrete is a fairly decent-sized job, like a small patio or a long sidewalk section.
How Cubic Feet Connect to Cubic Yards
Concrete bags tell you their volume in cubic feet. A cubic yard is much bigger than one cubic foot. How big?
- 1 foot x 1 foot x 1 foot = 1 cubic foot (1 cu ft)
- 3 feet x 3 feet x 3 feet = 27 cubic feet (27 cu ft)
So, one cubic yard holds the same amount as 27 cubic feet. This is the key number we use to go from the volume a bag makes (in cubic feet) to how many bags fill a cubic yard (27 cubic feet).
Figuring Out Bag Yields
Every concrete bag lists how much wet concrete it makes. This is its yield. Yield is very important. It tells you how much volume you get from one bag. This is the ‘how much concrete per bag’ information you need.
Common bag sizes and their typical yields in cubic feet are:
- 40-pound bag: Makes about 0.30 cubic feet
- 50-pound bag: Makes about 0.37 cubic feet
- 60-pound bag: Makes about 0.45 cubic feet
- 80-pound bag: Makes about 0.60 cubic feet
These numbers can vary slightly between brands. Always check the label on the bag you are buying. The label gives you the most accurate concrete yield per bag for that specific product.
The Math: Cubic Yards to Concrete Bags
Now we combine what we know. We need 27 cubic feet of concrete to fill one cubic yard. Each bag makes a certain number of cubic feet. To find out how many bags make 27 cubic feet, we just divide the total volume needed (27 cubic feet) by the volume one bag makes (its yield in cubic feet). This is how we calculate cubic yards to concrete bags.
The formula is simple:
Number of Bags = Total Cubic Feet Needed / Cubic Feet Per Bag
For one cubic yard, the total cubic feet needed is 27.
How Many 60 lb Concrete Bags Per Yard?
A standard 60-pound bag typically yields about 0.45 cubic feet.
Number of Bags = 27 cubic feet / 0.45 cubic feet per bag
Number of Bags = 60 bags
So, you typically need 60 of the 60 lb concrete bags per yard.
How Many 80 lb Concrete Bags Per Yard?
A standard 80-pound bag typically yields about 0.60 cubic feet.
Number of Bags = 27 cubic feet / 0.60 cubic feet per bag
Number of Bags = 45 bags
So, you typically need 45 of the 80 lb concrete bags per yard.
Bags Per Cubic Yard Summary Table
Here’s a quick table showing the typical numbers for common bag sizes for one cubic yard:
| Bag Size | Typical Yield (Cubic Feet) | Bags Per Cubic Yard (Calculated) |
|---|---|---|
| 40 pounds | 0.30 cu ft | 27 / 0.30 = 90 bags |
| 50 pounds | 0.37 cu ft | 27 / 0.37 = ~73 bags |
| 60 pounds | 0.45 cu ft | 27 / 0.45 = 60 bags |
| 80 pounds | 0.60 cu ft | 27 / 0.60 = 45 bags |
Note: The bag yield can vary slightly by brand. Always check the bag label.
Why the Numbers Can Change: Factors Affecting Yield
The numbers above are based on typical yields. But sometimes the amount of wet concrete you get from a bag can be slightly different. This is because of a few things:
- How much water you add: This is the biggest factor. Adding too much water makes the concrete weaker and can slightly change the volume you get. It might make it seem like you have a bit more volume at first, but it ruins the concrete’s strength. Adding the correct amount of water shown on the bag is key for getting the right volume and strong concrete.
- Mixing: How well you mix also plays a small role.
- Air content: Some mixes have air added (air-entrainment) to help with freezing and thawing. This changes the yield a bit. Standard concrete bags usually don’t have much added air compared to ready-mix concrete from a truck.
For basic projects with standard concrete bags, sticking to the water amount on the bag will give you a yield very close to what the bag says.
Estimating Your Concrete Yardage
Before you can figure out how many bags you need, you must know how much concrete your project requires. This is called estimating concrete yardage or finding the volume of concrete per yard needed. Most projects are simple shapes, like squares or rectangles (for slabs, patios, sidewalks) or long rectangles (for footings).
To find the volume, you need three measurements:
- Length
- Width
- Depth (or Thickness)
Make sure all your measurements use the same units. It’s easiest to measure everything in feet.
- Measure the length in feet.
- Measure the width in feet.
- Measure the depth or thickness in inches, then convert inches to feet by dividing by 12.
Example: You want to pour a concrete slab that is 10 feet long, 10 feet wide, and 4 inches thick.
- Length = 10 feet
- Width = 10 feet
- Depth = 4 inches. Convert to feet: 4 inches / 12 inches/foot = 0.333 feet (about one-third of a foot).
Now, multiply these three numbers together to get the volume in cubic feet:
Volume in Cubic Feet = Length (ft) × Width (ft) × Depth (ft)
Volume = 10 feet × 10 feet × 0.333 feet
Volume = 33.3 cubic feet
This is the total volume you need in cubic feet.
Converting Cubic Feet to Cubic Yards
Your bag calculations are based on cubic yards (27 cu ft per yard). So, you need to change your project volume from cubic feet to cubic yards.
To do this, divide your total cubic feet volume by 27 (since there are 27 cubic feet in 1 cubic yard).
Volume in Cubic Yards = Total Cubic Feet / 27
Using the example above (33.3 cubic feet):
Volume in Cubic Yards = 33.3 cubic feet / 27 cubic feet per yard
Volume in Cubic Yards = 1.23 cubic yards
So, your 10ft x 10ft x 4-inch slab needs about 1.23 cubic yards of concrete.
Calculating Concrete Bags Needed
Once you know the total volume needed in cubic yards (or cubic feet), you can calculate concrete bags needed.
Method 1: Using Cubic Feet Needed
This is the most direct way if you calculated your project size in cubic feet.
Number of Bags = Total Project Volume (in cubic feet) / Yield Per Bag (in cubic feet)
Using the 33.3 cubic feet example, and assuming you use 80 lb bags (yielding 0.60 cu ft each):
Number of Bags = 33.3 cu ft / 0.60 cu ft per bag
Number of Bags = 55.5 bags
You can’t buy half a bag, so you always round up. You would need 56 bags.
If using 60 lb bags (yielding 0.45 cu ft each):
Number of Bags = 33.3 cu ft / 0.45 cu ft per bag
Number of Bags = 74 bags
Method 2: Using Cubic Yards Needed
First, find your total cubic yards needed (we got 1.23 cubic yards). Then, multiply that number by the bags needed per cubic yard for your chosen bag size.
Using the 1.23 cubic yards example:
-
If using 80 lb bags (45 bags per yard):
Number of Bags = 1.23 cubic yards * 45 bags per cubic yard
Number of Bags = 55.35 bags. Round up to 56 bags. -
If using 60 lb bags (60 bags per yard):
Number of Bags = 1.23 cubic yards * 60 bags per cubic yard
Number of Bags = 73.8 bags. Round up to 74 bags.
Both methods give you the same answer, which is good!
Planning Your Project: Ordering Extra
You did the math! You know the ideal number of bags. But it’s always a good idea to order a bit more concrete than your calculation shows. Why?
- Waste: Some concrete might spill during mixing or pouring.
- Uneven Ground: The ground you pour on might not be perfectly flat or level. This means some spots will need slightly more concrete than planned.
- Getting the Depth Right: It can be hard to get the exact thickness everywhere, especially in a small area. You might pour a little thicker in some spots.
- Small Mistakes: Maybe your measurements were slightly off.
- Finishing Touches: Sometimes you need just a little extra to fill a low spot or finish the edge perfectly.
Running out of concrete mid-pour is a big problem. You can’t easily stop and go get more, especially if the concrete you’ve already poured is starting to set. It’s much better to have a few bags left over at the end.
A common rule is to add an extra 10% to 15% to your bag count.
Using the example needing 56 bags (80 lb):
- 10% extra: 56 * 0.10 = 5.6 bags. Add 6 bags. Total = 56 + 6 = 62 bags.
- 15% extra: 56 * 0.15 = 8.4 bags. Add 9 bags. Total = 56 + 9 = 65 bags.
Ordering between 62 and 65 bags of the 80 lb size for this project would be smart.
Using the example needing 74 bags (60 lb):
- 10% extra: 74 * 0.10 = 7.4 bags. Add 8 bags. Total = 74 + 8 = 82 bags.
- 15% extra: 74 * 0.15 = 11.1 bags. Add 12 bags. Total = 74 + 12 = 86 bags.
Ordering between 82 and 86 bags of the 60 lb size would be smart.
It’s worth checking the price difference between bag sizes. Sometimes buying 80 lb bags is cheaper per cubic foot of yield than 60 lb bags, even though the individual bag costs more. You also have fewer bags to lift and mix with the 80 lb size for the same volume.
Using a Concrete Mix Calculator
Math isn’t everyone’s favorite thing. Luckily, you don’t have to do all these calculations by hand. Many websites and home improvement stores offer a concrete mix calculator. This tool makes calculating concrete bags needed much easier.
How they work:
- You tell the calculator the shape of your project (square, rectangle, circle, tube for footings, etc.).
- You enter the measurements (length, width, depth) using the units you measured in (feet, inches, yards).
- You might select the size of the concrete bag you plan to use (like 60 lb or 80 lb).
- You click “calculate.”
The calculator will then tell you:
- The total volume of concrete needed in cubic feet.
- The total volume of concrete needed in cubic yards (the volume of concrete per yard needed).
- The estimated number of concrete bags required based on the bag size you picked and its typical yield.
Using a calculator helps avoid math mistakes and speeds up the planning process. It’s a great tool for estimating concrete yardage and figuring out cubic yards to concrete bags.
More Complex Shapes
What if your project isn’t a simple rectangle? Maybe it’s a circle for a hot tub pad, or a footing with a round bottom (a pier footing), or a set of stairs.
- Circles: You need the radius (distance from the center to the edge) and the depth. The area of a circle is π (pi, about 3.14) times the radius squared (radius * radius). Volume is Area * Depth. Volume = π * radius² * depth. Make sure radius and depth are in feet. Then divide by 27 for cubic yards.
- Tubes/Cylinders (for piers): You need the radius (half the diameter of the tube) and the height/depth of the tube. The volume calculation is the same as a circle’s area times the height. Volume = π * radius² * height. Measure in feet. Divide by 27 for cubic yards.
For more complex shapes, finding an online concrete calculator specific to that shape is the easiest way. Or you might break the shape down into simpler rectangles and circles, calculate the volume of each part, and add them together.
Grasping the Cost
Knowing how many bags per yard helps you estimate the cost. You just multiply the number of bags you need (including the extra for waste) by the price per bag.
For our example needing about 1.23 cubic yards:
- Using 80 lb bags (need 56 ideal, plan for 62-65): If an 80 lb bag costs $5, the cost is 65 bags * $5/bag = $325.
- Using 60 lb bags (need 74 ideal, plan for 82-86): If a 60 lb bag costs $4, the cost is 86 bags * $4/bag = $344.
In this example, the 80 lb bags might be slightly cheaper per yard, and you handle fewer bags. This comparison (cost per bag vs. yield per bag) is part of smart estimating.
Keep in mind, buying a large amount of concrete (several cubic yards) from a ready-mix concrete company that delivers a truck is often cheaper per cubic yard than buying many, many bags. However, for small projects needing only 1 or 2 cubic yards, bags are usually more convenient and cost-effective because you avoid delivery fees and minimum order sizes for trucks.
Getting the Best Results from Your Bags
Just knowing how many bags to buy isn’t the whole story. To make sure you get the right yield and strong concrete, remember these simple points:
- Use the Right Amount of Water: This is critical. Too much weakens the concrete. Follow the instructions on the bag carefully. It usually gives a range; aim for the lower end of the range for stronger concrete, adding just enough water to make it workable.
- Mix Completely: Make sure all the dry powder is mixed with water evenly. There should be no dry pockets.
- Prepare the Area: Make sure your forms are strong and correctly sized. The ground should be level and compacted. This helps ensure your actual volume matches your planned volume.
When you mix the concrete correctly and prepare your area, the yield from each bag will be close to what the manufacturer states, making your bag count accurate.
Bags vs. Ready-Mix
For very small jobs (a fence post, a stepping stone), one or two bags are perfect. For medium jobs (a small patio, a sidewalk section, footings for a deck), using bags is very common, and knowing how many bags are in a yard of concrete is essential for planning. For large jobs (a house foundation, a large driveway), ordering ready-mix concrete by the cubic yard from a truck is almost always the way to go. You order it directly in cubic yards, and the truck delivers the wet concrete ready to pour.
Frequently Asked Questions (FAQ)
h4: What is ‘Yield’ when talking about concrete bags?
Yield means how much wet concrete you get from one dry bag of mix after adding the correct amount of water. It’s usually measured in cubic feet. It tells you the volume of concrete per bag.
h4: Does the actual yield always match what the bag says?
It should be very close if you follow the instructions, especially the water amount. Adding too much water is the main reason the yield might seem different or the concrete isn’t as strong.
h4: Is a 60 lb bag or an 80 lb bag better?
Neither is strictly “better” in terms of concrete quality if mixed right. The 80 lb bag gives you more volume per bag (0.60 cu ft vs 0.45 cu ft). This means you need fewer bags total (45 vs 60 per yard) and do less mixing work for the same amount of concrete. However, 80 lb bags are heavier to lift and carry. Pick the size that is easiest for you to handle while also considering the total cost per yard.
h4: How much does a cubic yard of concrete weigh?
Wet concrete is heavy! One cubic yard weighs about 3,500 to 4,000 pounds (1.75 to 2 tons). This shows why using a truck is necessary for very large projects and why lifting many bags is hard work.
h4: Can I mix partial bags?
It’s best to mix whole bags to ensure the right mix proportions. If you only need a very small amount to finish, carefully estimate the fraction of the bag and reduce the water proportionally.
h4: How much water do I add to a bag?
Check the instructions on the concrete bag! The amount varies by mix and size, but it’s usually given as a range (e.g., 5 to 6 quarts per 80 lb bag). Using the right amount is critical for strength and yield.
h4: Is 45 bags of 80 lb concrete exactly one cubic yard?
It’s a very good estimate based on typical yields. Small variations in yield or your pouring area might mean you use slightly more or less in reality. That’s why planning for 10-15% extra bags is important.
h4: How do I calculate bags needed for a depth given in inches?
First, convert your depth in inches to feet by dividing by 12. For example, 6 inches is 6/12 = 0.5 feet. Then use this depth (in feet) along with your length and width (in feet) to calculate cubic feet, and convert to cubic yards or calculate bags from there.
Conclusion
Determining how many bags are in a yard of concrete boils down to knowing the volume of one cubic yard (27 cubic feet) and the volume of wet concrete each bag makes (the concrete yield per bag, usually listed on the bag in cubic feet). By dividing 27 by the bag’s yield, you find the number of bags needed per cubic yard (typically 45 for 80 lb bags and 60 for 60 lb bags).
For any project, start by estimating concrete yardage needed by measuring your area’s volume. Then, calculate concrete bags needed based on your chosen bag size and always plan to order a little extra to cover any shortages. Using a concrete mix calculator can help simplify these steps. With simple math and checking the bag label, you can accurately figure out cubic yards to concrete bags and get your project done right.