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.
Frequently Asked Questions
How many 80 lb bags are in half a yard of concrete?
Half a cubic yard is 13.5 cubic feet. Each 80 lb bag yields about 0.60 cubic feet, so you need 13.5 divided by 0.60, which equals 22.5 bags. Round up to 23 bags to have enough. At 60 lb bags (0.45 cu ft each), the same half yard needs about 30 bags.
Is it cheaper to buy bags or order ready-mix concrete?
Ready-mix is almost always cheaper once you reach about one cubic yard. At that point you are buying 45 bags of 80 lb mix, roughly 3,600 pounds of material, plus your time to haul and mix them. A ready-mix truck costs $130 to $180 per cubic yard delivered, and the quality is more consistent because the whole pour is one batch. For smaller pours, bags win on convenience and no minimum order.
How much water goes in an 80 lb bag of concrete?
About 3 pints, or just under half a gallon. Add the water gradually and mix until the concrete reaches a peanut butter consistency: thick enough to hold its shape but wet enough to pour and fill the form. Too much water weakens the finished concrete. The hydration chemistry depends on the exact water-to-cement ratio, so follow the bag directions rather than guessing by appearance.
How much does a cubic yard of concrete weigh?
About 4,000 pounds, or 2 tons. This is why ready-mix trucks carry 8 to 10 cubic yards maximum: a full load weighs 16 to 20 tons. For small projects, the practical implication is that bags add up fast. Forty-five 80 lb bags equal one cubic yard and weigh 3,600 pounds before water is added.
Should I add extra concrete for waste?
Yes, add 5 to 10 percent. Even a perfect form has imperfect spots at the edges, and a small shortage mid-pour can affect the slab’s strength at that joint. For hand-mixed bag pours, it is easy to mix one or two extra bags and keep them dry as a reserve rather than stopping to run back to the store. For ready-mix, order to the nearest quarter yard above your calculated need.
How long does bagged concrete take to set?
Standard bagged concrete reaches initial set in 2 to 3 hours and is walkable in 24 hours. Full cure takes 28 days. Fast-setting products like Quikrete Fast-Setting Concrete achieve initial set in 20 to 40 minutes and are weight-bearing in 4 hours, which is useful for fence posts and mailboxes where you need to backfill and move on quickly.