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Know Exactly How Many Bags Is A Yard Of Concrete
How many bags is a yard of concrete? Knowing this helps you buy the right amount for your project. It takes around 45 80lb bags or around 60 60lb bags of concrete mix to make one cubic yard of concrete. This number can change a little based on the exact mix and how you add water. This guide will help you figure out exactly how many bags you need using a simple cubic yards to bags conversion.
Getting Started: What is a Cubic Yard?
Before we talk about bags, let’s know what a cubic yard is. A cubic yard is a measure of volume. Think of a box that is 3 feet wide, 3 feet long, and 3 feet high. The space inside that box is one cubic yard.
How big is that in smaller units?
* 1 foot = 12 inches
* 1 yard = 3 feet
* So, 1 cubic yard = 3 feet * 3 feet * 3 feet
* 1 cubic yard = 27 cubic feet
This number, 27 cubic feet, is very important. Most concrete bags tell you how much volume they make in cubic feet. So, we often convert cubic yards to cubic feet first. Knowing how many cubic feet in a yard is the first big step in calculating concrete needed.
Knowing Your Concrete Bags: Size and Yield
Concrete mix comes in bags. The bags are sold by weight. The most common sizes are 60 pounds and 80 pounds. You might also see 40-pound or 50-pound bags. The concrete bag size (weight) helps you know how much mix you are buying by weight, but it does not tell you the volume of concrete you get after mixing it with water.
What “Yield” Means
This is where the word “yield” comes in. The concrete yield per bag means the amount of mixed concrete you get from one bag. It’s the volume of concrete per bag. Bag makers usually print this number on the bag. They usually give it in cubic feet.
Why is yield important? Because you need a certain volume of concrete to fill a space (like a slab or footing). You don’t need a certain weight of mixed concrete. The yield tells you the volume you get from each bag.
Common Bag Yields
The yield can be slightly different between brands and types of concrete mix. But there are typical numbers for the most common bag sizes:
- 80 lb bag: This bag usually yields about 0.6 cubic feet of mixed concrete.
- 60 lb bag: This bag usually yields about 0.45 cubic feet of mixed concrete.
- 50 lb bag: This bag usually yields about 0.375 cubic feet of mixed concrete.
- 40 lb bag: This bag usually yields about 0.3 cubic feet of mixed concrete.
Let’s focus on the 60 lb and 80 lb bags, as they are the most used for bigger home projects.
- The 60 lb concrete bag yield is about 0.45 cubic feet.
- The 80 lb concrete bag yield is about 0.6 cubic feet.
Keep in mind, these are typical numbers. Always check the bag itself if you can. The bag will have the most exact yield number for that specific mix.
Figuring Out Bags Per Cubic Yard
Now we can do the cubic yards to bags conversion. We know:
- A cubic yard is 27 cubic feet.
- A common bag yields a certain number of cubic feet when mixed.
To find out how many bags make one cubic yard, we just divide the total volume needed (27 cubic feet) by the volume one bag gives (the yield).
Let’s do the math for the two common sizes:
For 80 lb Bags:
- Total cubic feet needed for 1 yard = 27 cubic feet
- Yield per 80 lb bag = 0.6 cubic feet
- Number of 80 lb bags for 1 yard = Total cubic feet / Yield per bag
- Number of 80 lb bags = 27 cubic feet / 0.6 cubic feet per bag
- Number of 80 lb bags = 45 bags
So, it takes about 45 80lb bags to make one cubic yard of concrete.
For 60 lb Bags:
- Total cubic feet needed for 1 yard = 27 cubic feet
- Yield per 60 lb bag = 0.45 cubic feet
- Number of 60 lb bags for 1 yard = Total cubic feet / Yield per bag
- Number of 60 lb bags = 27 cubic feet / 0.45 cubic feet per bag
- Number of 60 lb bags = 60 bags
So, it takes about 60 60lb bags to make one cubic yard of concrete.
Factors That Change the Number of Bags
The numbers we just found (45 for 80lb, 60 for 60lb) are good rules of thumb. But the actual number you need might be slightly different. Why? A few things can affect the final volume you get from a bag:
- How Much Water You Add: The yield on the bag is based on adding the right amount of water. Adding too much water makes the concrete weaker. It can also change the final volume a little, though usually not a lot. Adding too little makes it hard to work with. Stick to the water amount on the bag instructions.
- Mixing Well: Making sure the concrete is mixed completely helps get the full yield from the bag.
- Waste: You always have some waste. Some concrete sticks to the wheelbarrow or mixer. Some might spill. Some might be left in the bag. It’s wise to plan for a little extra.
- Bag Variation: Even though they try to be exact, there can be tiny differences in the mix from one bag to the next.
Because of these factors, it’s a good idea to buy a few extra bags. People often add 5% to 10% extra to their calculated number. This is part of estimating concrete for projects wisely.
Table of Bag Needs Per Cubic Yard
Here is a quick table showing the number of bags needed for common volumes, based on the typical yields (0.6 cu ft for 80lb, 0.45 cu ft for 60lb). Remember to add a few extra bags for safety!
| Cubic Yards | Cubic Feet (Cubic Yards * 27) | Approx. 80 lb Bags (Cubic Feet / 0.6) | Approx. 60 lb Bags (Cubic Feet / 0.45) |
|---|---|---|---|
| 0.5 | 13.5 | 22.5 (Buy 23 or 24) | 30 (Buy 31 or 32) |
| 1 | 27 | 45 (Buy 47 or 48) | 60 (Buy 63 or 64) |
| 1.5 | 40.5 | 67.5 (Buy 70 or 71) | 90 (Buy 94 or 95) |
| 2 | 54 | 90 (Buy 95 or 96) | 120 (Buy 125 or 126) |
| 2.5 | 67.5 | 112.5 (Buy 118 or 119) | 150 (Buy 157 or 158) |
| 3 | 81 | 135 (Buy 141 or 142) | 180 (Buy 189 or 190) |
Always round up to the next whole bag. The “Buy” column suggests adding a little extra (around 5%).
Estimating Concrete for Your Project Area
Most projects don’t come in neat 1-cubic-yard sizes. You need to figure out the concrete volume calculation for your specific area. This lets you calculate concrete needed accurately.
The most common shapes are:
- Rectangular or Square (like a patio or walkway)
- Long and Thin (like a footing)
- Round (like a post hole)
Let’s look at how to find the volume for each. The goal is to get the volume in cubic feet first. Then you can convert to bags.
Calculating Volume for Slabs (Rectangles/Squares)
For a slab like a patio, sidewalk, or floor, you need to measure three things:
* Length
* Width
* Thickness (or depth)
Make sure all your measurements are in the same units. Feet are easiest because the yield is in cubic feet.
Example: You want to pour a patio that is 10 feet long, 8 feet wide, and 4 inches thick.
-
Measure:
- Length = 10 feet
- Width = 8 feet
- Thickness = 4 inches
-
Convert Units: The length and width are in feet. The thickness is in inches. We need to change inches to feet. There are 12 inches in 1 foot.
- Thickness in feet = Thickness in inches / 12
- Thickness in feet = 4 inches / 12 = 0.333 feet (we can round this to 0.34 for simple math, or keep it as 4/12 or 1/3)
-
Calculate Volume in Cubic Feet: Volume = Length * Width * Thickness
- Volume = 10 feet * 8 feet * 0.333 feet
- Volume = 80 * 0.333 cubic feet
- Volume ≈ 26.64 cubic feet
-
Convert Cubic Feet to Bags: Now you have the volume in cubic feet (about 26.64 cu ft). Use the yield of your bag size. Let’s say you are using 80 lb bags (yield = 0.6 cu ft).
- Number of bags = Total cubic feet / Yield per bag
- Number of 80 lb bags = 26.64 cu ft / 0.6 cu ft per bag
- Number of 80 lb bags ≈ 44.4 bags
-
Round Up and Add Extra: You can’t buy part of a bag. Always round up to the next whole bag.
- Round 44.4 bags up to 45 bags.
- Now, add a little extra for safety (say, 5%). 45 bags * 0.05 = 2.25 bags. Round up to 3 extra bags.
- Total bags to buy = 45 + 3 = 48 bags.
If you used 60 lb bags (yield = 0.45 cu ft):
* Number of 60 lb bags = 26.64 cu ft / 0.45 cu ft per bag
* Number of 60 lb bags ≈ 59.2 bags
* Round up to 60 bags.
* Add 5% extra: 60 bags * 0.05 = 3 bags.
* Total bags to buy = 60 + 3 = 63 bags.
Notice that 26.64 cubic feet is very close to 27 cubic feet (which is one cubic yard). So, our bag counts (48 for 80lb, 63 for 60lb) are close to our earlier numbers for a full cubic yard (45-47 for 80lb, 60-63 for 60lb), after adding extra. This confirms our calculations make sense.
Simple Steps for Slabs:
* Measure Length (in feet).
* Measure Width (in feet).
* Measure Thickness (in inches).
* Convert Thickness to feet (inches / 12).
* Multiply Length * Width * Thickness (in feet) to get volume in cubic feet.
* Divide volume in cubic feet by your bag’s yield (0.6 for 80lb, 0.45 for 60lb).
* Round up to the next whole bag.
* Add 5-10% more bags for safety.
Calculating Volume for Footings (Long and Thin)
Footings are like very long, thin slabs. You still use Length * Width * Depth.
* Length (in feet)
* Width (in feet or inches)
* Depth (in feet or inches)
Again, convert all numbers to feet before multiplying.
Example: You need a footing that is 50 feet long, 16 inches wide, and 8 inches deep.
-
Measure:
- Length = 50 feet
- Width = 16 inches
- Depth = 8 inches
-
Convert Units: Convert width and depth to feet.
- Width in feet = 16 inches / 12 = 1.333 feet (or 16/12 = 4/3 feet)
- Depth in feet = 8 inches / 12 = 0.666 feet (or 8/12 = 2/3 feet)
-
Calculate Volume in Cubic Feet: Volume = Length * Width * Depth
- Volume = 50 feet * 1.333 feet * 0.666 feet
- Volume ≈ 50 * 0.888 cubic feet
- Volume ≈ 44.4 cubic feet
-
Convert Cubic Feet to Bags: Using 80 lb bags (yield = 0.6 cu ft).
- Number of 80 lb bags = 44.4 cu ft / 0.6 cu ft per bag
- Number of 80 lb bags ≈ 74 bags
-
Add Extra: Add 5% extra. 74 bags * 0.05 = 3.7 bags. Round up to 4 extra bags.
- Total bags to buy = 74 + 4 = 78 bags.
Using 60 lb bags (yield = 0.45 cu ft):
* Number of 60 lb bags = 44.4 cu ft / 0.45 cu ft per bag
* Number of 60 lb bags ≈ 98.6 bags
* Round up to 99 bags.
* Add 5% extra: 99 bags * 0.05 = 4.95 bags. Round up to 5 extra bags.
* Total bags to buy = 99 + 5 = 104 bags.
Simple Steps for Footings:
* Measure Length (in feet).
* Measure Width (in inches or feet).
* Measure Depth (in inches or feet).
* Convert Width and Depth to feet if needed (inches / 12).
* Multiply Length * Width * Depth (all in feet) to get volume in cubic feet.
* Divide volume in cubic feet by your bag’s yield.
* Round up to the next whole bag.
* Add 5-10% more bags for safety.
Calculating Volume for Post Holes (Round)
For round holes like fence post holes, you need the diameter (distance across the circle) and the depth.
-
Measure:
- Diameter of the hole (in inches or feet)
- Depth of the hole (in inches or feet)
-
Convert Units: Convert both to feet. Also, you need the radius, which is half the diameter.
- Diameter in feet = Diameter in inches / 12
- Radius in feet = Diameter in feet / 2
- Depth in feet = Depth in inches / 12
-
Calculate Volume in Cubic Feet: The area of a circle is Pi (π) times the radius squared (radius * radius). Pi is about 3.14. The volume of a cylinder (a post hole is like a cylinder) is the area of the circle times the depth.
- Volume = Pi * Radius * Radius * Depth
- Volume ≈ 3.14 * (Radius in feet) * (Radius in feet) * (Depth in feet)
Example: You need to fill a post hole that is 12 inches across and 3 feet deep.
-
Measure:
- Diameter = 12 inches
- Depth = 3 feet
-
Convert Units:
- Diameter in feet = 12 inches / 12 = 1 foot
- Radius in feet = 1 foot / 2 = 0.5 feet
- Depth in feet = 3 feet (already in feet)
-
Calculate Volume in Cubic Feet:
- Volume = 3.14 * 0.5 feet * 0.5 feet * 3 feet
- Volume = 3.14 * 0.25 * 3 cubic feet
- Volume ≈ 0.785 * 3 cubic feet
- Volume ≈ 2.355 cubic feet
-
Convert Cubic Feet to Bags: Using 80 lb bags (yield = 0.6 cu ft).
- Number of 80 lb bags = 2.355 cu ft / 0.6 cu ft per bag
- Number of 80 lb bags ≈ 3.925 bags
-
Round Up and Add Extra: Round 3.925 bags up to 4 bags. Add extra (maybe one extra bag for this small amount).
- Total bags to buy = 4 + 1 = 5 bags.
Using 60 lb bags (yield = 0.45 cu ft):
* Number of 60 lb bags = 2.355 cu ft / 0.45 cu ft per bag
* Number of 60 lb bags ≈ 5.23 bags
* Round up to 6 bags. Add extra (maybe one extra bag).
* Total bags to buy = 6 + 1 = 7 bags.
Simple Steps for Post Holes:
* Measure Diameter (in inches or feet).
* Measure Depth (in inches or feet).
* Convert both to feet if needed (inches / 12).
* Find the Radius (Diameter in feet / 2).
* Calculate Volume = 3.14 * Radius * Radius * Depth (all in feet).
* Divide volume in cubic feet by your bag’s yield.
* Round up to the next whole bag.
* Add 5-10% more bags for safety.
Why Getting the Number Right Matters
- Saves Money: Buying too many bags costs more money. You might not use the extra bags for a long time, and they can go bad if they get wet.
- Avoids Waste: Unused bags or leftover mixed concrete are waste. You have to deal with throwing them away.
- Finishes the Job: Running out of concrete in the middle of a pour is a big problem. You need to stop, go buy more bags, and the new batch might not mix quite the same or bond well to the already setting concrete. It’s much better to have a few bags left over than not enough.
- Better Project Planning: Knowing the bag count helps you plan the work. You know how many bags you need to move, open, and mix.
This careful estimating concrete for projects and concrete volume calculation is a key part of doing the job well.
Putting It All Together: Steps to Buy the Right Amount
Here is a step-by-step guide to figure out how many bags you need for any project:
- Measure Your Project Area: Use a tape measure to find the length, width, and depth (or thickness) of the area you want to fill with concrete.
- Choose Your Units: Decide if you will work in feet or inches. Feet are usually easier for the final volume calculation, as bag yield is in cubic feet.
- Convert All Measurements to the Same Unit: If you measured in inches, divide by 12 to get feet. If you have different units, make them all the same (e.g., all feet).
- Calculate the Volume: Multiply length by width by depth (for rectangles/squares/footings). For round holes, use the Pi * radius * radius * depth formula. This gives you the volume in cubic feet.
- Find Your Bag’s Yield: Look on the concrete bag you plan to buy. Find the “yield” number in cubic feet. If it’s not there, use the typical numbers: 0.6 cu ft for 80 lb bags, 0.45 cu ft for 60 lb bags.
- Divide Volume by Yield: Divide the total volume (in cubic feet) you calculated in Step 4 by the yield per bag (in cubic feet) from Step 5. This tells you the exact number of bags needed.
- Round Up: You must buy full bags. Always round the number from Step 6 up to the nearest whole bag.
- Add Extra: Add an extra 5% to 10% to the rounded number. This covers waste and makes sure you don’t run short. Round this final number up again if needed.
- Buy the Bags: You now have the number of bags to buy!
Following these steps will help you get very close to the exact number of bags you need.
Frequently Asked Questions (FAQ)
Here are some common questions people ask about concrete bags and volume.
h4 How accurate are the yield numbers on the bags?
Bag makers try to be accurate. The yield number on the bag is the best number to use for that specific product. However, the actual volume you get can change a little based on how much water you add and how well you mix it. Using the bag’s number and adding 5-10% extra bags is the most reliable method.
h4 Can I mix partial bags of concrete?
It’s best to mix full bags if you can. The mix inside the bag (cement, sand, gravel) can separate a little during shipping and handling. If you take out only part of a bag, you might get more of one material than another. This can make your concrete weaker or harder to work with. If you must mix a partial bag, try to stir the dry mix in the bag first to make it uniform.
h4 What if my project needs less than one cubic yard?
Most home projects use less than a cubic yard. Our examples for the patio (about 26.64 cu ft) and the footing (about 44.4 cu ft) were less than 27 cubic feet (1 yard). You still use the same steps: calculate your project volume in cubic feet, find the bag yield in cubic feet, divide your volume by the yield, round up, and add extra. The conversion method works for any volume, not just full yards.
h4 What if I need more than one cubic yard?
If your project is much bigger, like a large patio or a driveway, you might need many cubic yards. For these jobs, it’s often cheaper and easier to order ready-mix concrete delivered by a truck. The company sells it by the cubic yard. You tell them how many cubic yards you need, and they mix and deliver it. Our method here is mostly for smaller jobs where using bags makes sense.
h4 Does the type of concrete mix change the yield?
Yes, different types of concrete mix (like standard concrete, high-strength concrete, or quick-setting concrete) might have slightly different amounts of sand and gravel. This can change the yield per bag a little. That’s why checking the specific bag you are buying for its yield is important. Always use the yield number printed on the bag if it’s there.
h4 Is there a simple way to estimate quickly?
Yes, if you just need a quick guess:
* One 80 lb bag makes about 0.6 cubic feet.
* One 60 lb bag makes about 0.45 cubic feet.
* One cubic yard is 27 cubic feet.
Divide 27 by the bag’s yield to get the number of bags per yard (27 / 0.6 = 45 for 80lb; 27 / 0.45 = 60 for 60lb). This gives you the base number. Remember to calculate your project volume accurately in cubic feet first, then convert.
h4 Can I use a concrete calculator tool online?
Yes, many websites and hardware stores have online concrete calculators. These tools are very helpful. You usually enter your project’s shape and measurements (length, width, depth) and the bag size you plan to use. The calculator does the math for you and tells you how many bags to buy. They often include a little extra for waste too. Use one of these tools to double-check your own calculations. Just make sure you input the correct measurements and select the right bag size and its specific yield if possible.
Final Thoughts
Knowing how many bags of concrete make a yard, or more importantly, how to figure out how many bags you need for your specific project, is a key skill for any DIY concrete job. It’s not just about dividing 27 cubic feet by a bag’s yield. You need to measure your area carefully, convert units correctly, calculate the volume in cubic feet, find the yield of your specific bag, do the division, round up, and add a little extra for safety.
By following the steps for concrete volume calculation and using the concrete yield per bag information, you can confidently calculate concrete needed and buy the right number of bags for your job. This saves you time, money, and stress, helping your concrete project go smoothly from start to finish.