Short answer: An 80 lb bag of concrete mix makes about 0.60 cubic feet, a 60 lb bag about 0.45, a 50 lb bag about 0.375 and a 40 lb bag about 0.30. A cubic yard of concrete takes 45 bags of 80 lb mix.
| Bag size | Cubic feet per bag | Bags per cubic yard | Area at 4 in thick |
|---|---|---|---|
| 40 lb | 0.3 | 90 | 0.9 sq ft |
| 50 lb | 0.375 | 72 | 1.13 sq ft |
| 60 lb | 0.45 | 60 | 1.35 sq ft |
| 80 lb | 0.6 | 45 | 1.8 sq ft |
Why the yield is not the weight
The size on the bag is the dry weight of the mix. Once you add water, the mix becomes a volume of wet concrete, and that volume is what the label calls the yield. Heavier bags yield proportionally more, so an 80 lb bag makes twice as much as a 40 lb bag.
Brands and mix types differ a little, so use the yield printed on the bag you buy. High-strength mixes and fast-setting mixes can have slightly different yields.
Using the yield to count bags
Find the volume of your pour in cubic feet, divide by the yield of one bag, and round up. For a slab, multiply the length by the width by the thickness in feet. Add about 10 percent for waste before you divide.
Worked example
A footing 20 ft long, 12 inches wide and 8 inches deep holds 13.3 cubic feet. At 0.60 cubic feet per 80 lb bag that is 22.2 bags, so buy 23 bags before any waste, or 25 with a small allowance.
Use the Concrete CalculatorEnter your own measurements and get an exact amount.
Frequently asked questions
How many cubic feet are in a 60 lb bag of concrete?
About 0.45 cubic feet.
How many cubic feet are in a 90 lb bag of concrete?
About 0.67 cubic feet on the labels of common brands, which is about 40 bags per cubic yard.
How many bags of concrete make 1 cubic foot?
About 1.7 bags of 80 lb mix, or 2.2 bags of 60 lb mix.
How many square feet does one 80 lb bag cover?
About 1.8 square feet at 4 inches thick, and 1.2 square feet at 6 inches.
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Figures are typical planning values. Material sizes, densities and local requirements vary, so confirm with your supplier before ordering.
Last updated October 11, 2026.