How Many Bags of Concrete Are in a Yard? 40, 50, 60 and 80 lb Chart
A cubic yard of concrete is 27 cubic feet, and every bag is labeled with the cubic feet it makes when mixed. Divide 27 by that number and you know how many bags fill a yard. Here is the chart, plus how to size up your own project.
Bags per cubic yard
| Bag size | Yield per bag | Bags per cubic yard |
|---|---|---|
| 40 lb | 0.30 cu ft | 90 |
| 50 lb | 0.375 cu ft | 72 |
| 60 lb | 0.45 cu ft | 60 |
| 80 lb | 0.60 cu ft | 45 |
Yields are close to what major brands print on their bags, but they vary slightly by product. Always use the number on your bag.
How far does one bag go?
A bag covers more area the thinner you pour it.
| Slab thickness | 60-lb bag | 80-lb bag |
|---|---|---|
| 2 in | 2.7 sq ft | 3.6 sq ft |
| 4 in | 1.35 sq ft | 1.8 sq ft |
| 6 in | 0.9 sq ft | 1.2 sq ft |
Example: a 10×10 foot slab
At 4 inches thick, a 10×10 slab is 33.3 cubic feet. Divide by 0.6 and you need about 56 bags of 80-lb mix. Add 10 percent extra for uneven ground and spillage, and the number rises to 62. Our concrete calculator does this for any size and shows 60-lb and 80-lb bag counts side by side.
Bags for fence posts
A 10-inch wide, 30-inch deep hole around a 4×4 post holds roughly 1.3 cubic feet of concrete, which is about two 80-lb bags per post. See our fence post guide for depth and spacing.
Bags or ready-mix delivery?
Bags are best for small jobs such as post holes, steps and small pads. For bigger pours, a truck can be easier and cheaper. A cubic yard takes 45 bags of 80-lb mix, which is a lot of lifting and mixing, and a slab needs to be poured before it starts to set. Ask a local supplier for a quote, including any short-load fee for small orders.
Common mistakes
- Using the wrong yield, since bag weight alone does not tell you the volume
- Forgetting waste allowance of about 10 percent
- Measuring thickness in inches but length and width in feet without converting
- Adding extra water to make mixing easier, which weakens the concrete
Work out the volume, divide by your bag's yield, round up, and add your waste allowance. For help choosing the thickness, read our slab thickness guide.
Enter the size of your slab to get cubic yards of concrete and the number of bags to buy.
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