If you have ever priced out a concrete project, you have run into the two ways concrete is sold: by the bag at the hardware store, and by the cubic yard from a ready-mix truck. Knowing how many bags equal a yard is the key to comparing the two and deciding which way to go.
The short answer
A cubic yard is 27 cubic feet of concrete. Each bag size yields a set amount, so the bags per yard work out like this:
| Bag size | Yield per bag | Bags per cubic yard |
|---|---|---|
| 80 lb | 0.60 cu ft | 45 |
| 60 lb | 0.45 cu ft | 60 |
| 40 lb | 0.30 cu ft | 90 |
So a cubic yard takes 45 bags of 80 pound, 60 bags of 60 pound, or 90 bags of 40 pound concrete mix. Those numbers are worth memorizing, because they turn any project into a quick comparison.
Why the yield matters more than the weight
It is tempting to assume two 40 pound bags equal one 80 pound bag. They do by weight, but what you actually care about is volume, and the yields line up exactly: two 40 pound bags at 0.30 cubic feet each give 0.60 cubic feet, the same as one 80 pound bag. When you are buying, always think in cubic feet of yield, not pounds.
Working a real example
Say you are pouring a small landing that comes to 12 cubic feet of concrete after you add a waste factor.
- In 80 pound bags: 12 divided by 0.60 is 20 bags
- In 60 pound bags: 12 divided by 0.45 is about 27 bags
- In 40 pound bags: 12 divided by 0.30 is 40 bags
Twenty 80 pound bags is a manageable afternoon with a mixer. Forty 40 pound bags is a lot more trips and a lot more mixing for the same result, which is why most people buy the largest bag they can comfortably lift.
When to stop bagging and call the truck
Mixing by the bag is fine for footings, post holes, and small pads. But the effort adds up fast. A single cubic yard is 45 bags of 80 pound mix, which is around 3,600 pounds of material to haul, open, and mix one bag at a time.
As a general rule, once a project passes about one cubic yard, ready-mix delivery is usually cheaper once you count your time, and the quality is more consistent because the whole pour is one uniform batch instead of dozens of hand-mixed bags. Below a yard, bags almost always win.
Do not forget the base
Whatever you pour, most slabs and pads want 4 to 6 inches of compacted gravel underneath for drainage and support. You can size that separately with our gravel calculator.
Let the calculator compare it for you
Our concrete calculator takes your dimensions, adds the waste factor, and returns the volume in cubic yards along with bag counts for 80, 60, and 40 pound bags, plus a bagged versus ready-mix cost comparison. For patios and floors specifically, the concrete slab calculator is set up for that exact pour.