How Many Bags of Concrete in a Cubic Yard? 40, 60 and 80 lb Bags

The quick answer

If you only need the numbers, here they are. These use common bag yields, so treat them as a guide.

So a full cubic yard needs about 90, 60 or 45 bags depending on the size you choose. The rest of this guide shows how those figures are worked out and how to use them for jobs that are not exactly one yard.

Where the numbers come from

There is only one idea here. A bag of mix makes a certain amount of concrete when you add water. That amount is its yield, and it is printed on the bag in cubic feet. A cubic yard is a fixed volume, 3 ft x 3 ft x 3 ft, which is 27 cubic feet.

So the count is simple division: bags per cubic yard = 27 / yield.

• 40 lb bag: 27 / 0.30 = 90 bags
• 60 lb bag: 27 / 0.45 = 60 bags
• 80 lb bag: 27 / 0.60 = 45 bags

Notice that the yield goes up in step with the weight. A 60 lb bag is one and a half times a 40 lb bag, and its yield is one and a half times larger as well.

What a yard weighs in bags

Here is a pattern that is easy to miss. Multiply the number of bags by the bag weight and you get the same answer each time.

• 90 bags x 40 lb = 3,600 lb
• 60 bags x 60 lb = 3,600 lb
• 45 bags x 80 lb = 3,600 lb

Each way of buying a cubic yard comes to about 3,600 lb of bagged mix. That is worth thinking about before the delivery arrives. You are not choosing between more concrete and less; you are choosing how that weight is split up.

It also gives you a feel for scale. A cubic yard is a lot of material to move by hand, whichever bag you pick.

Half a yard, two yards and a yard with waste

Few jobs are exactly one yard. Multiply the volume in cubic feet by the same division and round up.

Half a yard

Half a yard is 13.5 cubic feet. That is 13.5 / 0.30 = 45 bags of 40 lb, 13.5 / 0.45 = 30 bags of 60 lb, and 13.5 / 0.60 = 22.5 bags of 80 lb. You cannot buy half a bag, so round up to 23.

Two yards

Two yards is 54 cubic feet. That needs 180 bags of 40 lb, 120 bags of 60 lb or 90 bags of 80 lb.

One yard with a 10% waste allowance

Add 10% to a cubic yard and you have 29.7 cubic feet. That is 99 bags of 40 lb, 66 bags of 60 lb or 49.5 bags of 80 lb, which rounds up to 50.

If you do not have the volume yet, our guide on how much concrete you need for a slab shows how to get it from length, width and thickness.

Choosing a bag size

There is no single right answer. This short decision guide lays out the trade-off without putting prices on anything, since prices vary by place and product.

• Lighter bags (40 lb). Easier to lift and carry, and easier to handle if you are working alone or in a tight spot. The cost is a much higher number of bags to open, stack and mix.
• Middle bags (60 lb). A compromise in both weight and count.
• Heavier bags (80 lb). Far fewer bags for the same volume, which means less opening and less stacking, but each one is harder to move.

Ask yourself three questions. Can you comfortably lift the bag? How many bags can you store and keep dry? And how long do you want to spend mixing? The answers usually point to a size.

For a large pour, stop and ask a local ready-mix supplier what they would suggest. They can advise on whether delivered concrete suits the job, and we do not make that call here. When your total reaches a couple of cubic yards, moving 3,600 lb or more of bags per yard is a serious task.

Leftover bags and rounding

Rounding up means you will often finish with more mix than the exact volume needs. That is normal, and it is small. For the half-yard example, 23 bags of 80 lb make 23 x 0.60 = 13.8 cubic feet against the 13.5 you needed, so about 0.3 cubic feet is spare.

Sometimes the count comes out even. A full cubic yard in 80 lb bags is exactly 45 bags, which is 45 x 0.60 = 27 cubic feet with nothing to spare. That is a good reason to add a waste allowance, so that a perfectly even count does not leave you a single bag short.

Whole bags also mean that the three sizes can finish at slightly different spare volumes for the same job. If you are close to the edge, compare them before you decide.

Check the bag you actually buy

The yields in this guide are common figures, not guarantees. A different product may print a different yield, and then every number above changes with it. Read the label, find the yield in cubic feet and substitute it into 27 / yield.

You can do this in our Concrete Slab Calculator, which uses 0.30, 0.45 and 0.60 for the three bag sizes. If your bag differs, work out the count by hand with the division above. The Home and Energy Calculators page lists related tools, and if your project has a roof, see how to calculate rafter length.

Frequently asked questions

Tools used in this guide

• Concrete Slab Calculator

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Photo: Brett Jordan on Unsplash