How Many Bags of Concrete to Make a Yard: The Ultimate Guide

To determine how many bags of concrete you need to make a cubic yard, you first need to know how much concrete is in a bag and the concrete mix per yard. Generally, you’ll need around 56 to 90 bags of concrete, depending on the bag size and the specific mix. This guide will help you with estimating concrete bags for your project, whether you’re a seasoned pro or tackling a DIY concrete volume calculation.

Deciphering Concrete Bag Yields

The question of “how many bags of concrete to make a yard” is a common one for anyone planning a concrete project. A cubic yard is a standard unit of volume, often used in construction. Understanding how much concrete in a bag is the first step in accurately calculating your needs. Concrete bags come in various sizes, most commonly 40 lb, 60 lb, and 80 lb. The yield of each bag – how much mixed concrete it produces – directly impacts the total number of bags you’ll need.

Bag Sizes and Their Corresponding Yields

The amount of concrete a bag yields is not just about its weight; it’s about the density of the dry mix and the water added during mixing. Manufacturers provide estimated yields for their products.

60 lb Bag Concrete Yield: A typical 60 lb bag of concrete mix will yield approximately 0.45 cubic feet of concrete when mixed according to instructions.
80 lb Bag Concrete Yield: An 80 lb bag of concrete mix generally yields about 0.60 cubic feet of concrete.
40 lb Bags: While less common for larger projects, 40 lb bags will yield about 0.30 cubic feet.

These are average figures. Always check the specific product packaging for the most accurate yield information, as different brands and types of concrete mixes can have slightly varying yields.

Calculating Your Concrete Needs: The Cubic Yard Breakdown

A cubic yard is a substantial amount of concrete. It’s equal to 27 cubic feet. To figure out how many bags you need, you’ll divide the total volume you need (in cubic feet) by the yield of a single bag (in cubic feet).

The Conversion to Cubic Feet

1 cubic yard = 27 cubic feet

This conversion is fundamental for all your calculations. When you’re working with bagged concrete coverage, you’ll be dealing with cubic feet per bag, and you’ll need to scale that up to the 27 cubic feet that make up a cubic yard.

Step-by-Step Bag Estimation

Let’s break down the process of estimating concrete bags:

Determine Your Project Volume: Measure the dimensions (length, width, and depth) of the area you need to fill with concrete. Ensure all measurements are in the same unit (e.g., feet).
Calculate Volume in Cubic Feet: Multiply length × width × depth.
- Example: For a 4 ft x 8 ft slab that is 4 inches deep:
  - Convert depth to feet: 4 inches / 12 inches/foot = 0.33 feet
  - Volume = 4 ft × 8 ft × 0.33 ft = 10.56 cubic feet
Convert Project Volume to Cubic Yards (Optional but Recommended): Divide your cubic feet volume by 27.
- Example: 10.56 cubic feet / 27 cubic feet/cubic yard = 0.39 cubic yards
Determine Bags Needed Per Cubic Yard: This is where the bag yield comes into play.
- For 60 lb bags (0.45 cu ft yield): 27 cu ft / 0.45 cu ft/bag = 60 bags per cubic yard.
- For 80 lb bags (0.60 cu ft yield): 27 cu ft / 0.60 cu ft/bag = 45 bags per cubic yard.
Calculate Total Bags: Multiply the number of cubic yards you need by the number of bags per cubic yard.
- Example (using 60 lb bags): If you need 1 cubic yard, you’ll need 60 bags. If you need 0.5 cubic yards, you’ll need 0.5 × 60 = 30 bags.

Practical Considerations for Estimating Concrete Bags

Add a Buffer: It’s always wise to purchase an extra 5-10% of bags than your calculation suggests. This accounts for spillage, over-excavation, or slight miscalculations. Running out of concrete mid-pour is a critical issue, so a little extra is better than too little.
Consistency of Mix: Ensure you use the correct amount of water as specified on the bag. Too much or too little water can affect the strength and yield of the concrete.
Compaction and Sub-base: The thickness of your concrete pour is critical. A well-compacted sub-base will also ensure you’re not over-excavating and creating a void that needs filling.

Using a Concrete Bag Calculator

For those who prefer digital assistance, a concrete bag calculator can be an invaluable tool. These online calculators simplify the DIY concrete volume calculation process. You typically input your project’s dimensions (length, width, and depth), and the calculator automatically determines the volume in cubic feet and yards. It will then use pre-programmed data for common bag sizes (60 lb, 80 lb) to tell you precisely how many bags you need.

Features of a Good Concrete Bag Calculator

Dimension Input: Allows input in feet, inches, or even meters.
Bag Size Options: Lets you select from common bag weights (40 lb, 60 lb, 80 lb).
Yield Accuracy: Uses industry-standard yields for different bag sizes.
Waste Factor: May include an option to add a percentage for waste.
Unit Conversion: Seamlessly converts between imperial and metric units.

Finding the Right Concrete Volume Calculator

A concrete volume calculator is the tool that takes your measurements and translates them into the total volume of concrete required. Many construction supply websites and DIY blogs offer these free tools. When searching, look for terms like “concrete calculator,” “bagged concrete calculator,” or “cubic yard calculator.”

Factors Affecting Concrete Yield

While the general rules of thumb for how much concrete in a bag are useful, several factors can influence the actual yield:

Water-to-Cement Ratio

The amount of water added during mixing is perhaps the most critical factor. The water-to-cement ratio affects not only the workability of the concrete but also its final strength and yield.

Too Much Water: Makes the concrete easier to mix and pour but weakens it and can slightly increase the yield. However, this is generally discouraged as it compromises quality.
Too Little Water: Makes the concrete stiff and difficult to work with, potentially leading to poor consolidation and a lower yield.

Always follow the manufacturer’s recommendations precisely.

Aggregate Size and Density

The type and size of aggregates (sand and gravel) used in the concrete mix also play a role. Denser aggregates or mixes with a higher proportion of fine aggregates might slightly alter the yield compared to a mix with larger, lighter aggregates. While you usually don’t control this with pre-mixed bags, it’s a factor for bulk concrete.

Compaction and Air Entrapment

During the mixing and pouring process, air can become trapped within the concrete. Proper consolidation techniques (like tamping or using a vibrator) help remove these air pockets, resulting in a denser, stronger concrete and potentially a slightly lower final volume than if significant air were trapped.

Common Project Scenarios and Bag Calculations

Let’s look at some typical DIY projects and how to estimate the number of bags.

Small Projects: How Many Bags for a Sidewalk Section

Imagine you need to pour a small section of a sidewalk, say 3 feet wide, 5 feet long, and 4 inches deep.

Volume in Cubic Feet:
- Length = 5 ft
- Width = 3 ft
- Depth = 4 inches / 12 = 0.33 ft
- Volume = 5 ft × 3 ft × 0.33 ft = 4.95 cubic feet
Estimating Bags:
- Using 60 lb bags (0.45 cu ft yield): 4.95 cu ft / 0.45 cu ft/bag = 11 bags. Add 10% for safety: 11 × 1.10 = 12.1 bags. Round up to 13 bags.
- Using 80 lb bags (0.60 cu ft yield): 4.95 cu ft / 0.60 cu ft/bag = 8.25 bags. Add 10% for safety: 8.25 × 1.10 = 9.075 bags. Round up to 10 bags.

Medium Projects: Estimating for a Small Patio Slab

A 6 ft x 8 ft patio slab poured 4 inches thick.

Volume in Cubic Feet:
- Length = 8 ft
- Width = 6 ft
- Depth = 4 inches / 12 = 0.33 ft
- Volume = 8 ft × 6 ft × 0.33 ft = 15.84 cubic feet
Estimating Bags:
- Using 60 lb bags (0.45 cu ft yield): 15.84 cu ft / 0.45 cu ft/bag = 35.2 bags. Add 10%: 35.2 × 1.10 = 38.72 bags. Round up to 39 bags.
- Using 80 lb bags (0.60 cu ft yield): 15.84 cu ft / 0.60 cu ft/bag = 26.4 bags. Add 10%: 26.4 × 1.10 = 29.04 bags. Round up to 30 bags.

Larger Projects: How Many Bags to Make a Yard for a Driveway Section

Let’s consider a 10 ft x 10 ft section of a driveway poured 4 inches thick.

Volume in Cubic Feet:
- Length = 10 ft
- Width = 10 ft
- Depth = 4 inches / 12 = 0.33 ft
- Volume = 10 ft × 10 ft × 0.33 ft = 33 cubic feet
Estimating Bags:
- Using 60 lb bags (0.45 cu ft yield): 33 cu ft / 0.45 cu ft/bag = 73.33 bags. Add 10%: 73.33 × 1.10 = 80.66 bags. Round up to 81 bags.
- Using 80 lb bags (0.60 cu ft yield): 33 cu ft / 0.60 cu ft/bag = 55 bags. Add 10%: 55 × 1.10 = 60.5 bags. Round up to 61 bags.

Making a Full Cubic Yard

If you need exactly 1 cubic yard (27 cubic feet) of concrete:

Using 60 lb bags (0.45 cu ft yield): 27 cu ft / 0.45 cu ft/bag = 60 bags.
Using 80 lb bags (0.60 cu ft yield): 27 cu ft / 0.60 cu ft/bag = 45 bags.

Remember, these are ideal scenarios. Always factor in that extra bag or two.

When to Consider Bulk Concrete vs. Bagged Concrete

For larger projects, the question of how many bags of concrete to make a yard can become overwhelming. This is often the tipping point where ordering ready-mix concrete from a supplier becomes more economical and practical.

Pros of Bagged Concrete

Smaller Projects: Ideal for repairs, small patios, footings, or steps.
Convenience: Can be purchased and transported easily by individuals.
Control: You control the mixing process, which can be beneficial for specific applications.
No Minimum Order: You buy only what you need, unlike bulk orders.

Cons of Bagged Concrete

Labor Intensive: Mixing many bags by hand or with a small mixer is physically demanding.
Color Consistency: Achieving a uniform color across a large area poured from many small batches can be challenging.
Cost per Yard: For large volumes, the cost per cubic yard of bagged concrete is significantly higher than bulk concrete.
Time Consuming: Mixing dozens or hundreds of bags can take a considerable amount of time.

Pros of Bulk Concrete (Ready-Mix)

Efficiency: Delivered to your site in a ready-to-pour state, saving immense labor.
Consistency: Mixed in a controlled environment, ensuring uniform strength and quality.
Cost-Effective for Large Jobs: Cheaper per cubic yard for volumes exceeding 1-2 cubic yards.
Color Uniformity: Easier to achieve consistent color across a large pour.

Cons of Bulk Concrete

Requires Planning: You need to schedule delivery and have the site prepared.
Minimum Orders: Suppliers usually have minimum order quantities.
Site Access: The truck needs to be able to reach your pour site, or you’ll need a pump.
Potential for Waste: If your estimate is off, you might have leftover concrete you have to pay for or dispose of.

When is the switch typically made? For projects requiring more than approximately 1.5 to 2 cubic yards of concrete, it’s usually more cost-effective and practical to order ready-mix. For instance, if your calculation shows you need 90 bags (roughly 1.5 cubic yards using 60 lb bags), you’re approaching the threshold where bulk might be considered.

Tips for Successful Bagged Concrete Mixing and Pouring

Whether you’re using a few bags or many, proper technique is essential for a strong, durable concrete finish.

Mixing Techniques

Start with Water: Always add some water to the mixing container (wheelbarrow, mixer) before adding the dry mix. This prevents dry powder from sticking to the bottom.
Gradual Addition: Add the dry concrete mix gradually while continuously mixing.
Achieve the Right Consistency: Aim for a workable mix that is not too wet or too dry. It should hold its shape when squeezed but not crumble. A common analogy is the consistency of thick oatmeal or peanut butter.
Don’t Over-Mix: Over-mixing can weaken the concrete. Mix only until the ingredients are uniformly combined.
Use a Mixer for Larger Batches: For more than a few bags, a mechanical mixer (like a mortar mixer or a drum mixer) will save your back and ensure a more consistent mix.

Pouring and Finishing

Prepare the Site: Ensure the area is excavated to the correct depth and compacted. Install forms securely.
Moisten the Sub-base: Lightly dampen the sub-base and forms before pouring. This prevents them from absorbing water from the fresh concrete, which can weaken it.
Pouring: Start pouring from one end and work your way across, ensuring concrete fills all corners of the forms.
Consolidation: Use a shovel or tamper to consolidate the concrete, working it into corners and around any reinforcement. This helps remove air pockets.
Screeding: Use a straight edge (like a 2×4) to strike off excess concrete and create a level surface.
Floating and Troweling: Once the surface water has evaporated, use a float to smooth the surface and then a trowel for a final finish.
Curing: This is critical for strength. Keep the concrete moist for several days (ideally 7 days) by covering it with plastic sheeting, burlap, or applying a curing compound.

Frequently Asked Questions (FAQ)

Q1: How much concrete does a bag of concrete make?
A1: The amount a bag makes varies by weight. A 60 lb bag typically yields about 0.45 cubic feet, and an 80 lb bag yields about 0.60 cubic feet.

Q2: How many 80 lb bags of concrete are in a cubic yard?
A2: There are approximately 45 bags of 80 lb concrete mix in one cubic yard.

Q3: How many 60 lb bags of concrete are in a cubic yard?
A3: There are approximately 60 bags of 60 lb concrete mix in one cubic yard.

Q4: Can I mix concrete in a wheelbarrow?
A4: Yes, you can mix concrete in a wheelbarrow for small jobs (1-2 bags at a time). For larger quantities, a mechanical mixer is highly recommended for efficiency and consistency.

Q5: What happens if I add too much water to the concrete mix?
A5: Adding too much water weakens the concrete, making it less durable and susceptible to cracking. While it might seem easier to mix, it compromises the structural integrity of the final product.

Q6: How do I calculate concrete for an irregular shape?
A6: For irregular shapes, try to break them down into simpler geometric forms (squares, rectangles, circles) or approximate them. You can also use online concrete volume calculator tools that may offer more advanced input options, or consult with a professional for complex shapes.

Q7: Is bagged concrete good enough for a driveway?
A7: Bagged concrete can be used for small driveway repairs or small driveway sections. However, for an entire driveway, especially if it needs significant depth and strength, ordering bulk ready-mix concrete is generally more economical and provides a more consistent, durable result. The sheer volume of bags required for a full driveway would be impractical and labor-intensive.

Q8: What is the difference between concrete mix and mortar mix?
A8: Concrete mix is designed for structural applications and contains larger aggregates (gravel) for strength. Mortar mix is primarily sand and cement, designed for bonding bricks, blocks, or stones, and does not contain large aggregates.

By using this guide and the available tools, you can confidently estimate the number of concrete bags needed for your next project, ensuring you have the right amount for a successful pour.