So, you’re wondering, “How many bags of concrete in a yard?” You’ll need approximately 4 to 5 bags of 80 lb concrete or 6 to 7 bags of 60 lb concrete to make one cubic yard of concrete. This guide will help you figure out exactly how much concrete you need for your project and how to get it. We’ll cover everything from calculating your needs to making smart purchasing decisions.
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Figuring Out Your Concrete Needs
When you have a project that requires concrete, like a small patio, a new step, or a foundation for a shed, the first big question is often about the quantity. You don’t want to buy too much and have leftover material that might not store well, nor do you want to run out halfway through your pour, which can lead to weak spots and an unsightly finish. This is where understanding how much concrete you need, or how much concrete, becomes crucial.
The Basics of Concrete Volume: Cubic Yards
Concrete is typically sold and measured in cubic yards. A cubic yard is a unit of volume, representing a cube that is three feet long, three feet wide, and three feet tall (3 ft x 3 ft x 3 ft = 27 cubic feet). Most concrete calculators and pricing are based on this measurement.
Why Bagged Concrete?
For smaller DIY projects, bagged concrete is often the most convenient option. It comes pre-mixed with the right proportions of cement, sand, and aggregate. All you need to do is add water and mix. This eliminates the need for a large mixer or the complexity of ordering a concrete truck for small jobs. However, it’s important to know the concrete bag yield, which is the amount of concrete a single bag will produce once mixed with water.
Calculating Concrete Volume for Your Project
To determine how many bags of concrete you’ll need, you first need to calculate the volume of the space you intend to fill with concrete. This involves measuring the dimensions of your project and using a simple formula.
The Formula for Volume
The basic formula for calculating volume is:
Volume = Length × Width × Height
However, you need to be careful about your units. Since concrete is measured in cubic yards, and you’ll likely be measuring your project in feet and inches, you’ll need to convert your measurements.
Converting Units
- Inches to Feet: Divide the number of inches by 12. For example, 6 inches is 6/12 = 0.5 feet.
- Feet to Yards: Divide the number of feet by 3.
- Cubic Feet to Cubic Yards: Divide the volume in cubic feet by 27 (since 1 cubic yard = 27 cubic feet).
Example Calculation:
Let’s say you want to pour a concrete slab that is:
* Length: 10 feet
* Width: 8 feet
* Height (or thickness): 4 inches
- Convert height to feet: 4 inches / 12 inches/foot = 0.33 feet
- Calculate volume in cubic feet: 10 feet × 8 feet × 0.33 feet = 26.4 cubic feet
- Convert cubic feet to cubic yards: 26.4 cubic feet / 27 cubic feet/cubic yard = 0.98 cubic yards
So, for this slab, you need almost exactly one cubic yard concrete.
Using a Concrete Calculator
To simplify this process, many websites offer a concrete mix calculator or a bag concrete calculator. These tools allow you to input your project’s dimensions (length, width, thickness) and will automatically calculate the total cubic yard concrete needed. They often also factor in a small overage to account for uneven surfaces or waste.
Bags of Concrete Per Cubic Yard
Now that you know your project’s volume in cubic yards, you can figure out how many bags you’ll need. This depends on the size of the bag you are buying. The most common sizes are 80 lb bags and 60 lb bags.
80 lb Bags of Concrete
An 80 lb bag concrete typically yields about 0.60 cubic feet of mixed concrete.
To calculate how many 80 lb bags you need per cubic yard:
- Cubic feet per cubic yard: 27 cubic feet
- Cubic feet per 80 lb bag: 0.60 cubic feet
Calculation:
27 cubic feet / 0.60 cubic feet/bag = 45 bags
So, you will need approximately 45 bags of 80 lb concrete to make one cubic yard concrete.
60 lb Bags of Concrete
A 60 lb bag concrete typically yields about 0.45 cubic feet of mixed concrete.
To calculate how many 60 lb bags you need per cubic yard:
- Cubic feet per cubic yard: 27 cubic feet
- Cubic feet per 60 lb bag: 0.45 cubic feet
Calculation:
27 cubic feet / 0.45 cubic feet/bag = 60 bags
Therefore, you will need approximately 60 bags of 60 lb concrete to make one cubic yard concrete.
The Relationship: How Many Bags of Concrete in a Yard
Let’s summarize this in a clear table:
| Bag Size | Approximate Yield per Bag (Cubic Feet) | Bags Needed Per Cubic Yard |
|---|---|---|
| 80 lb bag | 0.60 cubic feet | 45 bags |
| 60 lb bag | 0.45 cubic feet | 60 bags |
Important Considerations for Bags of Concrete Needed
- Overage: It’s always wise to add 5-10% to your total bag count to account for waste, spills, or slight variations in your project’s dimensions and ground unevenness. So, if your calculation shows you need 45 bags, consider buying 47-50 bags.
- Bag Quality: Ensure you are buying good quality concrete mix. Stale or improperly stored concrete can affect its yield and strength.
- Water Amount: Follow the manufacturer’s instructions precisely for the amount of water to add. Too much or too little water can change the concrete bag yield and the final strength of the concrete.
Step-by-Step Guide to Ordering Bagged Concrete
Let’s walk through the process of determining your bags of concrete needed:
Step 1: Measure Your Project
- Measure the length of your project in feet.
- Measure the width of your project in feet.
- Measure the desired thickness (height) of your concrete in inches.
Step 2: Convert Measurements to Feet
- If your thickness is in inches, divide by 12 to get feet.
- Example: 6 inches / 12 = 0.5 feet
Step 3: Calculate Volume in Cubic Feet
- Multiply length × width × thickness (all in feet).
- Example: 10 ft × 8 ft × 0.5 ft = 40 cubic feet
Step 4: Convert Volume to Cubic Yards
- Divide your cubic feet total by 27.
- Example: 40 cubic feet / 27 = 1.48 cubic yards
Step 5: Determine Bag Quantity Based on Bag Size
- For 80 lb bags: Multiply your cubic yard total by 45.
- Example: 1.48 cubic yards × 45 bags/cubic yard = 66.6 bags. Round up to 67 bags.
- For 60 lb bags: Multiply your cubic yard total by 60.
- Example: 1.48 cubic yards × 60 bags/cubic yard = 88.8 bags. Round up to 89 bags.
Step 6: Add Overage
- Add an extra 5-10% to your total bag count.
- For 67 bags (80 lb): 67 × 1.05 = 70.35. Buy 71 bags.
- For 89 bags (60 lb): 89 × 1.05 = 93.45. Buy 94 bags.
So, for a 10 ft x 8 ft x 4 in slab, you would need approximately 71 bags of 80 lb concrete or 94 bags of 60 lb concrete. This process is often facilitated by a good concrete mix calculator.
What if Your Project Isn’t a Simple Rectangle?
Many projects aren’t perfect rectangles. Here’s how to handle common shapes:
Circular Slabs (Patios, Footings)
For a circular project, you’ll need the radius (half of the diameter) and the thickness.
- Volume of a Cylinder = π × radius² × height (where π ≈ 3.14)
Remember to convert all measurements to feet and then divide by 27 for cubic yards.
Example: A circular patio 8 feet in diameter with a 4-inch thickness.
- Radius: 8 ft / 2 = 4 ft
- Thickness in feet: 4 inches / 12 = 0.33 ft
- Volume in cubic feet: 3.14 × (4 ft)² × 0.33 ft = 3.14 × 16 sq ft × 0.33 ft = 16.57 cubic feet
- Volume in cubic yards: 16.57 cubic feet / 27 = 0.61 cubic yards
Now, use your bag concrete calculator logic:
- 80 lb bags: 0.61 cubic yards × 45 bags/cubic yard = 27.45 bags. Round up to 28 bags. Add 5% overage: 28 × 1.05 = 29.4. Buy 30 bags.
- 60 lb bags: 0.61 cubic yards × 60 bags/cubic yard = 36.6 bags. Round up to 37 bags. Add 5% overage: 37 × 1.05 = 38.85. Buy 39 bags.
Steps and Curbs
For steps or curbs, break them down into smaller rectangular or square sections. Calculate the volume of each section and add them together for your total volume.
Example: A simple step that is 3 feet long, 1 foot deep, and 6 inches high.
- Length: 3 ft
- Width (depth): 1 ft
- Height: 6 inches = 0.5 ft
- Volume in cubic feet: 3 ft × 1 ft × 0.5 ft = 1.5 cubic feet
- Volume in cubic yards: 1.5 cubic feet / 27 = 0.056 cubic yards
This is a small amount, and you’d be looking at needing just one or two bags for such a small addition.
Understanding Concrete Bag Yield Variations
While we’ve used general figures for concrete per bag yield, it’s important to know that these can vary slightly between brands and product lines. Always check the product packaging for the most accurate yield information. Some “concrete patch” or “repair” products will have a much smaller yield than general-purpose concrete mixes.
Factors Affecting Yield
- Water Content: As mentioned, adding more water than recommended will increase the volume slightly but will significantly reduce the strength.
- Bag Quality: Using a quality brand ensures you get the advertised yield.
- Mixing Consistency: Proper mixing helps achieve the designed volume.
How Much Concrete? The Importance of Precision
Getting how much concrete right is key to a successful project. Running out means a trip back to the store, potential delays, and the risk of a weak joint if the new concrete doesn’t bond well with the old. Buying too much means wasted money and effort in disposal.
Ordering Bulk Concrete vs. Bagged Concrete
For larger projects, ordering concrete by the cubic yard directly from a ready-mix concrete supplier is often more cost-effective and efficient.
When to Consider Bulk Concrete
- Large Projects: If your project requires more than about 10-15 cubic yard concrete, a concrete truck delivery might be cheaper per cubic yard.
- Time Savings: A truck can deliver a large volume quickly, reducing the labor-intensive process of mixing bags.
- Consistency: Bulk concrete is mixed at the plant with precise controls, ensuring consistent quality.
Comparing Costs
- Bagged Concrete: The cost per cubic yard can be significantly higher due to the packaging, transportation, and convenience factor. For example, if an 80 lb bag costs $7, then one cubic yard would cost 45 bags * $7/bag = $315.
- Bulk Concrete: The cost per cubic yard varies by region but might range from $120-$200, plus delivery fees.
You can use a concrete mix calculator to help compare the total cost of bagged concrete for your project versus the cost of bulk delivery.
The Mixing Process: Essential Tips
Once you’ve calculated how many bags of concrete in a yard (or for your specific project), you’ll need to mix it properly.
Tools for Mixing
- Wheelbarrow and Shovel: For small batches, a sturdy wheelbarrow and a shovel work well.
- Concrete Mixer: For larger projects using bags, renting a portable concrete mixer is highly recommended. It makes the process much faster and easier.
- Drill with Mixing Paddle: For very small repairs or patching, a heavy-duty drill with a special mixing paddle attachment can be used.
Mixing Steps
- Read Instructions: Always read the specific mixing instructions on the concrete bag.
- Add Water First (or partially): Some prefer to add about half the recommended water to the mixing container first.
- Add Concrete Mix: Gradually add the contents of the bag(s) to the water.
- Mix Thoroughly: Use your shovel or mixer to thoroughly combine the dry mix and water.
- Add Remaining Water: Slowly add more water, mixing continuously, until you reach the desired consistency. It should be workable but not soupy. The concrete bag yield is based on the recommended water amount.
- Check Consistency: A good mix will hold its shape when squeezed but will still be pliable enough to pour and spread.
What is the ideal consistency?
The ideal consistency is often described as “plastic” or “workable.” It should be moist enough to be molded and spread easily but not so wet that it separates or becomes runny. Over-watering is a common mistake that weakens the concrete.
Frequently Asked Questions (FAQ)
Q1: How many 60 lb bags of concrete are in a cubic yard?
A1: You need approximately 60 bags of 60 lb concrete to make one cubic yard. This is because a 60 lb bag typically yields about 0.45 cubic feet of concrete, and 27 cubic feet make a cubic yard (27 / 0.45 = 60).
Q2: How many 80 lb bags of concrete are in a cubic yard?
A2: You need approximately 45 bags of 80 lb concrete to make one cubic yard. An 80 lb bag usually yields about 0.60 cubic feet, and 27 cubic feet make a cubic yard (27 / 0.60 = 45).
Q3: What is the yield of a concrete bag?
A3: The yield of a concrete bag varies by size and brand. Typically, an 80 lb bag yields about 0.60 cubic feet, and a 60 lb bag yields about 0.45 cubic feet of mixed concrete. Always check the packaging for specific yield information.
Q4: Can I just mix concrete with water without measuring?
A4: It is highly recommended to measure the water carefully. Adding too much or too little water can significantly affect the strength and durability of the concrete, as well as its yield.
Q5: How do I calculate the amount of concrete for a non-rectangular area?
A5: For non-rectangular areas, break the shape down into simpler geometric forms (rectangles, squares, circles, triangles) and calculate the volume of each part separately. Then, add all the volumes together to get your total. A concrete mix calculator can be very helpful for complex shapes.
Q6: Should I buy extra bags of concrete?
A6: Yes, it is always advisable to purchase an additional 5-10% of concrete bags to account for waste, spills, uneven subgrade, or slight miscalculations in your volume estimate.
Q7: What is the difference between concrete mix and cement?
A7: Cement is a binder, a key ingredient in concrete. Concrete itself is a mixture of cement, sand (fine aggregate), gravel or crushed stone (coarse aggregate), and water. Bagged concrete mix already contains cement, sand, and aggregate in the correct proportions.
Q8: How much concrete does a bag of concrete make?
A8: This refers to the concrete bag yield. As mentioned, an 80 lb bag makes about 0.60 cubic feet, and a 60 lb bag makes about 0.45 cubic feet of concrete. This is crucial for calculating how much concrete you need for your project.
By following these guidelines and using the right tools, like a bag concrete calculator, you can confidently determine exactly how many bags of concrete you need for your next project, ensuring a strong and successful outcome.