Concrete Bag Calculator
Concrete Bag Calculator
Calculate how many 40 lb, 60 lb or 80 lb concrete bags are needed from project dimensions or a known volume.
Common Concrete Bag Yields
Concrete mix manufacturers can have slightly different yields. For estimating purposes, this calculator uses these common approximate values.
| Bag Size | Approximate Yield | Approx. Bags per Cubic Yard |
|---|---|---|
| 40 lb | 0.30 ft³ | 90 bags |
| 60 lb | 0.45 ft³ | 60 bags |
| 80 lb | 0.60 ft³ | 45 bags |
How the Concrete Bag Calculation Works
First, the calculator determines the volume of your project. For a rectangular area:
Volume = Length × Width × Depth
The selected waste allowance is added to the required volume. The final volume is then divided by the approximate yield of the selected bag size.
Because you cannot normally purchase a fraction of a concrete bag, the result is always rounded up to the next full bag.
40 lb vs 60 lb vs 80 lb Concrete Bags
40 lb Bags
Smaller bags can be easier to lift and handle, but more bags are required to complete the same project.
60 lb Bags
A 60 lb bag provides a middle ground between handling weight and total bag count.
80 lb Bags
Larger 80 lb bags reduce the total number of bags required, but each bag is significantly heavier to transport and mix.
Example
Suppose you are pouring a concrete slab that measures 10 feet long, 8 feet wide and 4 inches thick.
The project requires about 26.7 cubic feet of concrete before adding waste.
With a 10% waste allowance, approximately 29.3 cubic feet is required.
Using 80 lb bags with an approximate yield of 0.60 cubic feet each, you would need about 49 bags.
When Should I Consider Ready-Mix Concrete?
Bagged concrete can be very convenient for smaller pours because you can buy only the quantity you need and mix it on site. For larger pours, however, the time and labor required to transport and mix dozens or hundreds of bags can become substantial.
Compare the delivered cost of ready-mix with the total cost of bagged concrete, including your time, equipment and cleanup.
Frequently Asked Questions
Using an approximate yield of 0.60 cubic feet per bag, one cubic yard requires about 45 bags.
Using an approximate yield of 0.45 cubic feet per bag, one cubic yard requires about 60 bags.
Using an approximate yield of 0.30 cubic feet per bag, one cubic yard requires about 90 bags.
A small waste allowance is commonly useful because actual project dimensions and product yield may vary. The appropriate allowance depends on the project.
Bagged concrete can be practical for smaller projects. For larger pours, compare the cost and labor of mixing bags with local ready-mix delivery options.