People often ask, “Exactly how many bags of Portland cement per yard is it?” or “How many bags of Portland cement per yard do I need?” The quick answer is that there isn’t just one number. The amount changes based on the mix you need for your project. Most concrete uses between 5 and 8 bags of standard 94-pound Portland cement per cubic yard. Knowing how to estimate concrete needed helps you buy the right amount of materials.
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Grasping the Core Question
Making concrete is like baking. You need the right amounts of each part. These parts are Portland cement, sand, gravel or stone, and water. The cement is the glue. It holds everything together. When you mix these parts, they make concrete.
A cubic yard is a measure of space. Imagine a box that is 3 feet wide, 3 feet deep, and 3 feet tall. That box holds one cubic yard of material. When you order concrete from a ready-mix company, they sell it by the cubic yard. If you mix concrete yourself, you buy bags of cement, plus sand and gravel. You need to know how many bags make one cubic yard of concrete.
The number of bags depends on the concrete mix ratio. This ratio tells you how much cement, sand, and gravel to use. A common way to write this ratio is Cement : Sand : Gravel. For example, a 1:2:4 ratio means you use 1 part cement, 2 parts sand, and 4 parts gravel. The number of bags of cement per cubic yard changes with this ratio.
What is a Cubic Yard?
Let’s look closer at a cubic yard.
* It’s a cube.
* Each side measures 3 feet.
* The total size is 3 feet * 3 feet * 3 feet = 27 cubic feet.
So, one cubic yard is equal to 27 cubic feet. When you figure out how much concrete you need, you often measure your area in feet. Then you find the volume in cubic feet. After that, you divide the cubic feet by 27 to get cubic yards. This is a key step in cubic yard concrete calculation.
What is Portland Cement?
Portland cement is not a brand name. It’s a type of cement. It’s a very fine powder. It is made from materials like limestone and clay. These materials are heated in a kiln. This process makes clinker. The clinker is then ground into a fine powder. This powder is Portland cement.
When you add water to Portland cement, it reacts. This reaction is called hydration. It creates a paste. This paste coats the sand and gravel. As the paste hardens, it binds the sand and gravel together. This makes the hard material we call concrete.
Portland cement comes in bags. The standard bag size Portland cement in the United States is 94 pounds. This 94-pound bag is roughly equal to 1 cubic foot of cement powder by volume. This fact is very helpful when you figure out concrete mix ratios based on volume.
The Many Things That Change the Number of Bags
We said the number of bags is not fixed. Why is this? Many things affect it.
- The Concrete Mix Ratio: This is the most important factor. A mix with more cement is stronger. It uses more bags per yard. A mix with less cement uses fewer bags.
- Strength Needed: A sidewalk might use a weaker mix (fewer bags). A building foundation needs a stronger mix (more bags).
- Size of Gravel (Aggregate): The size and type of sand and gravel (aggregate) can change how much cement paste is needed to fill the spaces between them.
- Water Content: Using the right amount of water is key. Too much water makes weaker concrete. It also changes the volume slightly. We figure cement needs based on a standard amount of water for the mix design.
- Air Content: Some concrete mixes have tiny air bubbles added on purpose. This helps the concrete handle freezing and thawing. Adding air changes the total volume a little. This can slightly change the cement needed.
Grasping Concrete Mix Ratios
The concrete mix ratio is usually given as a ratio of volumes. It lists cement, sand, and gravel in that order.
* Cement : Sand : Gravel (or Stone)
Here are some common ratios and what they are often used for:
- 1 : 3 : 5: This is a lean mix. It has less cement. It’s good for simple jobs like filling fence post holes or small footings that don’t need much strength. It uses fewer cement bags per yard.
- 1 : 2 : 4: This is a very common mix. It’s called an all-purpose mix. It’s good for sidewalks, driveways, patios, and floor slabs for homes. It uses more cement than 1:3:5. So, it uses more bags per yard and makes stronger concrete.
- 1 : 1.5 : 3: This is a richer mix. It has more cement for its volume. It makes stronger concrete. It’s used for things like foundations, beams, and columns that hold up heavy loads. It uses the most cement bags per yard among these examples.
Knowing these ratios is important for mixing concrete proportions correctly.
Yield of Concrete Per Bag: Making Sense of It
Builders and material suppliers talk about the ‘yield’ of a mix. The yield of concrete per bag tells you how much concrete you get from one bag of cement when you use a specific mix ratio. It is usually measured in cubic feet.
Remember, one 94-pound bag of cement is about 1 cubic foot by volume. When you add sand, gravel, and water, the final volume of concrete is less than the total volume of the dry materials combined. This is because the sand fills the spaces between the gravel, and the cement paste fills the spaces between the sand and gravel.
Let’s look at the yield for common mixes using a 94-pound bag of cement:
- 1 : 3 : 5 Mix: A 94lb bag of cement mixed with 3 cubic feet of sand and 5 cubic feet of gravel. This mix typically yields about 5.5 to 6 cubic feet of wet concrete.
- 1 : 2 : 4 Mix: A 94lb bag of cement mixed with 2 cubic feet of sand and 4 cubic feet of gravel. This mix typically yields about 4.5 to 5 cubic feet of wet concrete.
- 1 : 1.5 : 3 Mix: A 94lb bag of cement mixed with 1.5 cubic feet of sand and 3 cubic feet of gravel. This mix typically yields about 3.8 to 4.2 cubic feet of wet concrete.
Note: These yield numbers are estimates. They can change slightly based on the type and moisture of the sand and gravel, and the amount of water added.
Calculating How Many Bags Per Yard
Now we can put it together to find the number of bags per cubic yard.
We know:
* 1 cubic yard = 27 cubic feet
* The yield of concrete per bag (in cubic feet) for a specific mix ratio.
To find the number of bags per cubic yard, you divide the total volume of a cubic yard (27 cubic feet) by the yield per bag (in cubic feet).
Number of Bags per Yard = 27 cubic feet / Yield per bag (in cubic feet)
Let’s use the estimated yields from the last section:
-
For a 1 : 3 : 5 Mix (Yield ~ 5.8 cubic feet per bag):
Number of Bags = 27 / 5.8
Number of Bags ≈ 4.66 bags
You would need about 5 bags (since you can’t buy parts of bags). -
For a 1 : 2 : 4 Mix (Yield ~ 4.8 cubic feet per bag):
Number of Bags = 27 / 4.8
Number of Bags ≈ 5.63 bags
You would need about 6 bags. -
For a 1 : 1.5 : 3 Mix (Yield ~ 4.0 cubic feet per bag):
Number of Bags = 27 / 4.0
Number of Bags = 6.75 bags
You would need about 7 bags.
So, based on common mixes, you can see the number of bags of Portland cement per yard is usually between 5 and 8 bags. A weaker mix uses fewer bags. A stronger mix uses more bags.
Here’s a table showing this:
Estimated Bags of Cement Per Cubic Yard
| Mix Ratio (Cement:Sand:Gravel) | Typical Yield per Bag (Cubic Feet) | Calculation (27 / Yield) | Estimated Bags per Cubic Yard | Common Use |
|---|---|---|---|---|
| 1 : 3 : 5 | ~5.5 – 6.0 | 27 / 5.8 (avg) | ~4.7 | Non-structural fill, light use |
| 1 : 2 : 4 | ~4.5 – 5.0 | 27 / 4.8 (avg) | ~5.6 | Sidewalks, Patios, Footings |
| 1 : 1.5 : 3 | ~3.8 – 4.2 | 27 / 4.0 (avg) | ~6.8 | Foundations, Slabs, Beams |
Note: These numbers are estimates. Always check local building codes or specific project needs.
This table helps make cubic yard concrete calculation clearer. It shows how the mix ratio directly impacts the number of bags.
How to Estimate Concrete Needed for Your Project
Before you buy materials, you need to know how much concrete you need. This is how to estimate concrete needed. You figure out the volume of the area you want to fill with concrete.
For simple shapes like squares, rectangles, or circles, you can use simple math.
Estimating Concrete for a Rectangular Area (Like a Patio or Walkway)
- Measure the Length: Measure how long the area is in feet.
- Measure the Width: Measure how wide the area is in feet.
- Measure the Thickness: Measure how deep the concrete needs to be. This must also be in feet. If your plan says 4 inches thick, you need to change inches to feet. 4 inches divided by 12 inches per foot = 0.333 feet.
- Calculate Volume in Cubic Feet: Multiply Length * Width * Thickness. This gives you the volume in cubic feet.
Volume (cubic feet) = Length (ft) * Width (ft) * Thickness (ft) - Convert to Cubic Yards: Divide the volume in cubic feet by 27 (since 1 cubic yard = 27 cubic feet).
Volume (cubic yards) = Volume (cubic feet) / 27
Example: Estimating Concrete for a 10 ft x 10 ft Patio, 4 inches thick
- Length = 10 feet
- Width = 10 feet
- Thickness = 4 inches = 4/12 feet = 0.333 feet
- Volume (cubic feet) = 10 ft * 10 ft * 0.333 ft = 33.3 cubic feet
- Volume (cubic yards) = 33.3 cubic feet / 27 cubic feet/yard ≈ 1.23 cubic yards
So, you would need about 1.25 cubic yards of concrete for this patio.
Estimating Concrete for a Circular Area (Like a Sonotube or Column)
- Measure the Diameter: Measure the distance across the circle through the center in feet.
- Find the Radius: Divide the diameter by 2. Radius = Diameter / 2.
- Measure the Height/Depth: Measure how tall or deep the circle is in feet.
- Calculate Volume in Cubic Feet: The formula for the volume of a cylinder is π * radius² * height. Use 3.14 for π.
Volume (cubic feet) = 3.14 * (Radius (ft))² * Height (ft) - Convert to Cubic Yards: Divide the volume in cubic feet by 27.
Volume (cubic yards) = Volume (cubic feet) / 27
Example: Estimating Concrete for a Post Hole, 1 foot wide, 4 feet deep
- Diameter = 1 foot
- Radius = 1 foot / 2 = 0.5 feet
- Height = 4 feet
- Volume (cubic feet) = 3.14 * (0.5 ft)² * 4 ft = 3.14 * 0.25 sq ft * 4 ft = 3.14 cubic feet
- Volume (cubic yards) = 3.14 cubic feet / 27 cubic feet/yard ≈ 0.116 cubic yards
So, you would need a bit more than 0.1 cubic yards for this post hole.
It’s always a good idea to add a little extra (say, 5-10%) to your estimate. This is because there can be waste, uneven ground, or slightly deeper spots. It’s better to have a little too much concrete than not enough.
Standard Bag Size Portland Cement and Cubic Feet Per Bag
As we talked about, the standard bag size Portland cement in the USA is 94 pounds. This weight is set by industry standards. This 94-pound bag has a volume close to 1 cubic foot when loose.
This fact is super helpful for concrete batch volume calculations, especially when you are mixing small amounts by hand or in a small mixer. Instead of weighing sand and gravel, people often measure them by volume using buckets or wheelbarrows.
If a mix ratio is 1:2:4 by volume, and you use one 94lb bag (which is about 1 cubic foot) of cement, you would then use:
* 2 cubic feet of sand
* 4 cubic feet of gravel
Knowing that one bag is about one cubic foot of cement makes it easy to figure out the amounts of sand and gravel based on the volume ratios.
Deciphering Cement Sand Gravel Ratio for Concrete
The cement sand gravel ratio for concrete is the recipe. It sets the strength and working traits of the concrete. It’s usually given by volume, but sometimes by weight. For small jobs using bagged cement, volume ratios are most common because it’s easier to measure sand and gravel by volume.
Here are the parts and why their amounts matter:
- Cement: This is the binder. More cement means a stronger mix. But too much cement can cause cracking.
- Sand (Fine Aggregate): Sand fills the spaces between the gravel. It helps make the mix smooth and workable. The right amount of sand helps prevent the larger gravel pieces from separating.
- Gravel (Coarse Aggregate): This gives the concrete its bulk and strength. Using gravel makes concrete much cheaper than if it was just cement and sand. The size of the gravel matters for different jobs. Smaller gravel is used for thinner slabs or where a smoother finish is needed. Larger gravel is used for thicker sections like footings.
The ratio you choose sets the concrete’s strength (measured in pounds per square inch or psi) after it hardens.
- Lower Strength (e.g., 2000-3000 psi): Often uses ratios like 1:3:5 or 1:2.5:4. These need fewer cement bags per yard. Good for patios, walkways, simple footings.
- Moderate Strength (e.g., 3000-4000 psi): Often uses ratios like 1:2:4 or 1:2:3.5. These need more cement bags per yard. Good for residential slabs, driveways, foundations.
- High Strength (e.g., 4000+ psi): Often uses richer ratios like 1:1.5:3 or even more cement. These need the most cement bags per yard. Used for structural beams, columns, industrial floors.
Understanding the cement sand gravel ratio for concrete is key to getting the right number of cement bags per yard and the right concrete strength.
Mixing Concrete Proportions
Once you have your ratio, you need to measure your materials correctly. This is mixing concrete proportions.
For small batches:
* You can use buckets or wheelbarrows.
* If your ratio is 1:2:4 and you use one 94lb bag of cement (about 1 cubic foot), you need:
* Cement: 1 bag (or 1 cubic foot)
* Sand: 2 cubic feet
* Gravel: 4 cubic feet
How do you measure cubic feet with a bucket? You can figure out the volume of your bucket. Or, more simply, you can measure how many buckets fill a known volume. For example, if you have a 5-gallon bucket, it holds about 0.67 cubic feet. So, for the 1:2:4 mix with one bag of cement:
* Sand (2 cubic feet): You need 2 / 0.67 ≈ 3 buckets of sand.
* Gravel (4 cubic feet): You need 4 / 0.67 ≈ 6 buckets of gravel.
So, a batch using one bag of cement with a 1:2:4 ratio is: 1 bag cement, 3 buckets sand, 6 buckets gravel, plus water.
For larger batches using a mixer, you’ll scale this up. A common small mixer might handle a batch made with 2 or 3 bags of cement at a time.
Concrete Batch Volume
Concrete batch volume is the amount of concrete you mix at one time. If you are mixing by hand or with a small mixer, your batch volume is small. If you order from a ready-mix plant, their batch volume is large (truckloads, measured in cubic yards).
When you are mixing yourself, you decide your concrete batch volume based on:
* The size of your mixer.
* How much concrete you need for that part of the job.
* How quickly you can place and finish the concrete before it starts to set.
If you need 1 cubic yard of 1:2:4 mix, and you calculated you need about 6 bags of cement, you could mix this in several batches. If your mixer can handle a 2-bag batch:
* You need a total of 6 bags.
* Each batch uses 2 bags.
* You will need 6 / 2 = 3 batches.
For each 2-bag batch of 1:2:4 mix:
* Cement: 2 bags (or about 2 cubic feet)
* Sand: 2 * 2 = 4 cubic feet
* Gravel: 2 * 4 = 8 cubic feet
You would measure out 4 cubic feet of sand and 8 cubic feet of gravel for each batch, plus water. This shows how the concrete batch volume relates to the total amount needed and your mixer size.
Fathoming Cubic Feet Per Bag Cement
We keep going back to the fact that a 94-pound bag of Portland cement is approximately 1 cubic foot in volume. This is a core idea for mixing concrete by volume.
Why is it only approximately 1 cubic foot? The exact volume of a powder can vary slightly based on how it’s packed. But for practical concrete mixing on a job site, using 1 cubic foot per 94-pound bag is accurate enough.
This relationship, cubic feet per bag cement, is what lets us easily use volume-based mix ratios (like 1:2:4) with standard bagged cement.
If you were buying materials by weight, you would need different ratios (e.g., by pounds or kilograms). Ready-mix plants often weigh ingredients for better control. But for DIY projects, volume is simpler, thanks to the standard bag size being close to 1 cubic foot.
Concrete Calculator Tool: Making it Easier
Doing these calculations can seem like a lot of work. This is where a concrete calculator tool comes in handy.
You can find many concrete calculator tools online. Most of them work like this:
1. You enter the shape and size of the area you need concrete for (e.g., a rectangle 10 ft x 10 ft x 4 inches thick).
2. You select the type of mix you plan to use (or the required strength). The tool usually knows the typical mix ratios and yields for common strengths.
3. The tool does the cubic yard concrete calculation for you.
4. It then uses the yield per bag for the chosen mix to tell you how many bags of cement, and how much sand and gravel (usually in cubic yards or tons), you need.
A concrete calculator tool simplifies how to estimate concrete needed. It helps you quickly figure out the materials based on your project size and desired concrete strength. It saves you from doing all the math yourself. But it’s still good to know how the math works, so you understand where the numbers come from.
More on Mix Designs and Their Impact
Let’s look at how changing the mix design really changes the number of bags and the concrete.
Example 1: A Sidewalk (moderate strength, 3000 psi)
- Common mix ratio: 1:2:4
- Estimated yield per bag: ~4.8 cubic feet
- Estimated bags per cubic yard: 27 / 4.8 ≈ 5.6 bags (order 6)
- If your sidewalk needs 2 cubic yards of concrete:
- Total bags needed: 2 yards * 6 bags/yard = 12 bags
- Total sand needed: 2 yards * (amount of sand per yard)
- Total gravel needed: 2 yards * (amount of gravel per yard)
To find the amount of sand and gravel per yard for a 1:2:4 mix:
A 1:2:4 mix uses 1 part cement, 2 parts sand, 4 parts gravel. Total parts by volume (excluding water) = 1+2+4 = 7 parts.
One bag of cement is 1 cubic foot. The yield is about 4.8 cubic feet.
The total dry volume used is 1+2+4 = 7 cubic feet. This 7 cubic feet of dry material makes about 4.8 cubic feet of wet concrete.
To get one cubic yard (27 cubic feet) of wet concrete, you need ~5.6 bags of cement.
If 5.6 bags is the ‘1’ part of the ratio for a cubic yard, then sand is ‘2’ parts and gravel is ‘4’ parts relative to the cement volume needed.
Let’s reframe. If 5.6 bags (~5.6 cubic feet of cement powder volume) make 1 cubic yard of concrete with a 1:2:4 mix, then:
* Sand needed = 5.6 (cement vol) * 2 (sand ratio) = 11.2 cubic feet of sand per cubic yard of concrete.
* Gravel needed = 5.6 (cement vol) * 4 (gravel ratio) = 22.4 cubic feet of gravel per cubic yard of concrete.
Check the volumes: 5.6 cf cement + 11.2 cf sand + 22.4 cf gravel = 39.2 cf dry ingredients. These compact to make 27 cf wet concrete. This confirms the yield concept – the wet volume is less than the sum of dry volumes.
So for 2 cubic yards of 1:2:4 mix:
* Cement: 12 bags (or order 13 to be safe)
* Sand: 2 yards * 11.2 cubic feet/yard = 22.4 cubic feet
* Gravel: 2 yards * 22.4 cubic feet/yard = 44.8 cubic feet
You would then order sand and gravel by cubic yards or tons. 22.4 cubic feet is about 0.83 cubic yards (22.4/27). 44.8 cubic feet is about 1.66 cubic yards (44.8/27).
Example 2: Simple Footings (lower strength, 2500 psi)
- Common mix ratio: 1:3:5
- Estimated yield per bag: ~5.8 cubic feet
- Estimated bags per cubic yard: 27 / 5.8 ≈ 4.66 bags (order 5)
- If your footings need 1.5 cubic yards of concrete:
- Total bags needed: 1.5 yards * 5 bags/yard = 7.5 bags (order 8)
Using the same logic for sand and gravel per yard:
If 4.66 bags (~4.66 cubic feet cement vol) make 1 cubic yard with a 1:3:5 mix, then:
* Sand needed = 4.66 * 3 = 13.98 cubic feet of sand per cubic yard.
* Gravel needed = 4.66 * 5 = 23.3 cubic feet of gravel per cubic yard.
For 1.5 cubic yards of 1:3:5 mix:
* Cement: 8 bags
* Sand: 1.5 yards * 13.98 cubic feet/yard = 20.97 cubic feet (~0.78 cubic yards)
* Gravel: 1.5 yards * 23.3 cubic feet/yard = 34.95 cubic feet (~1.3 cubic yards)
These examples show how crucial the concrete mix ratio is for figuring out the number of bags per yard and the amounts of sand and gravel needed.
Interpreting Ready-Mix vs. Bagged Concrete
Sometimes it’s easier to order ready-mix concrete, especially for large jobs. Ready-mix companies mix the concrete at their plant and deliver it in a truck. They sell it by the cubic yard.
When you order ready-mix, you tell them the strength you need (e.g., 3000 psi, 4000 psi). The ready-mix company has standard designs (ratios) to meet that strength. They use precise weights for materials, not just volumes, for better quality control. They also add admixtures (chemicals) for workability, curing time, or air content.
If you are doing a small job, buying bags of cement, sand, and gravel and mixing it yourself can be cheaper. It also lets you work at your own speed. However, it’s harder to get the exact same quality and strength as professionally mixed concrete.
Knowing how many bags of Portland cement per yard is useful whether you mix it yourself or order ready-mix. If you mix yourself, you need the number of bags to buy. If you order ready-mix, knowing the typical bag count per yard helps you understand the richness of the mix they are sending and what you are paying for in terms of cement content.
Getting Your Materials
Once you know how many bags of cement, and how much sand and gravel you need (in cubic feet or cubic yards), you can order your materials.
- Cement: Bought in 94-pound bags.
- Sand and Gravel: Often sold by the cubic yard or by the ton. You can buy small amounts in bags too, but buying in bulk (by the yard or ton) is much cheaper for larger amounts.
- Water: You’ll use tap water, but need enough of it.
When buying sand and gravel by the cubic yard, remember:
* 1 cubic yard of sand weighs about 2400-3000 pounds (1.2-1.5 tons), depending on moisture.
* 1 cubic yard of gravel weighs about 2500-3200 pounds (1.25-1.6 tons), depending on the type and size.
So, if you need 0.83 cubic yards of sand, you might order 1 cubic yard to be safe. If you need 1.3 cubic yards of gravel, you’d order 1.5 cubic yards. It’s always better to slightly overestimate your material needs. Leftover material can often be used elsewhere, but running short stops your work and can ruin a concrete pour.
Importance of Water and Admixtures
While the focus is on the solid parts, water is key. Using the right amount of water is critical for concrete strength and workability.
- Too much water: Makes concrete weak. It also causes more shrinkage as it dries, which can lead to cracks. The ratio of water to cement (called the water-cement ratio) is very important. Lower water-cement ratios make stronger concrete.
- Too little water: Makes the mix stiff and hard to work with. It might not fully hydrate the cement, also reducing strength.
Admixtures are chemicals added in small amounts. They change concrete properties.
* Water reducers: Let you use less water while keeping the mix workable. This improves strength.
* Air entrainers: Add tiny air bubbles. This improves resistance to freezing and thawing cycles.
* Set retarders or accelerators: Slow down or speed up how fast the concrete hardens.
These can affect the final volume slightly or change the optimal water content, indirectly influencing the practical yield and thus the number of bags needed for a specific performance. However, for standard calculations based on mix ratios, we usually use the basic cement, sand, gravel, and a standard amount of water assumed by the ratio.
FAQ: Answering More Questions
h4 How much does a cubic yard of concrete weigh?
A cubic yard of standard concrete weighs about 3500 to 4000 pounds (1.75 to 2 tons). This varies slightly based on the mix ratio and the type of stone used.
h4 Can I mix concrete by weight instead of volume?
Yes, mixing by weight is more accurate and is how ready-mix plants do it. However, for small jobs with bagged materials, measuring by volume is common and easier. You would need a scale and know the weight ratios for your desired mix.
h4 What happens if I use the wrong mix ratio?
Using too little cement will make the concrete weak. It might not last long or hold up to the planned use (like car traffic on a driveway). Using too much cement can make the mix sticky, hard to work with, and more likely to crack. Using the wrong amounts of sand or gravel affects workability and strength.
h4 Is there a difference between Portland cement and concrete mix?
Yes. Portland cement is just the binder (the powder in the bag). Concrete mix (like Sakrete or Quikrete) is a pre-mixed bag that contains Portland cement, sand, and gravel already combined in a specific ratio. You just add water. Concrete mix bags are much heavier than plain cement bags because they contain all the ingredients. A bag of concrete mix yields much less volume than a bag of cement because it’s the finished recipe. A 60-pound bag of concrete mix makes about 0.016 cubic yards, and an 80-pound bag makes about 0.022 cubic yards. You would need many more bags of concrete mix than bags of cement to make a cubic yard.
h4 Can I use a concrete calculator tool for any project?
Yes, most online concrete calculator tools can handle simple shapes like squares, rectangles, circles, and sometimes even tubes or footings. For complex shapes or large projects, you might need to break the area into simpler parts or get help from a professional estimator.
h4 How much sand and gravel do I need with the cement?
The amount of sand and gravel depends directly on the concrete mix ratio you choose and the total volume of concrete you need. For a 1:2:4 mix, you need about 2 cubic feet of sand and 4 cubic feet of gravel for every 1 cubic foot (one 94lb bag) of cement powder in the dry mix. When calculating for a cubic yard of wet concrete, you use the proportions relative to the cement bags needed per yard, as shown in the examples above (e.g., ~11.2 cubic feet sand and ~22.4 cubic feet gravel per cubic yard for a 1:2:4 mix).
In Summary
Figuring out exactly how many bags of Portland cement per yard you need is not a single answer. It starts with knowing what a cubic yard is (27 cubic feet). Then you choose the right concrete mix ratio for your job. Common ratios like 1:3:5, 1:2:4, and 1:1.5:3 need different amounts of cement.
You use the estimated yield of concrete per bag for your chosen mix (how much wet concrete one 94-pound bag makes, usually 4-6 cubic feet). Then you divide 27 cubic feet (one yard) by that yield number. This tells you the estimated bags per cubic yard.
- 1:3:5 mix: about 5 bags per yard
- 1:2:4 mix: about 6 bags per yard
- 1:1.5:3 mix: about 7 bags per yard
Remember that a standard bag size Portland cement is 94 pounds and about 1 cubic foot by volume. This helps when figuring out your mixing concrete proportions for sand and gravel based on the volume ratios.
You also learned how to estimate concrete needed for your project size. Measuring your area in feet, finding the volume in cubic feet, and dividing by 27 gives you cubic yards.
Using a concrete calculator tool can make these cubic yard concrete calculation steps easier.
Always round up the number of bags you buy. It’s better to have a little extra material than not enough. With the right planning based on your chosen cement sand gravel ratio for concrete and total concrete batch volume, you can get the right amount of materials for a successful concrete project.