How Many Bags of Concrete Are in a Cubic Yard?
A cubic yard of concrete takes 45 bags of 80-lb mix, 60 bags of 60-lb mix or 90 bags of 40-lb mix, because a yard is 27 cubic feet and an 80-lb bag yields about 0.60. A 10 by 10 foot slab at 4 inches needs 1.23 yards, or 56 bags.
The short answer
Concrete is sold two ways: by the cubic yard from a ready-mix truck, and by the bag as dry mix you blend with water. To compare them you need one conversion. A cubic yard holds 27 cubic feet, and each bag yields a known volume once mixed. Divide 27 by the bag's yield and you have the bag count.
| Bag size | Yield per bag | Bags per cubic yard | Bag weight total |
|---|---|---|---|
| 80 lb | 0.60 cu ft | 45 | 3,600 lb |
| 60 lb | 0.45 cu ft | 60 | 3,600 lb |
| 40 lb | 0.30 cu ft | 90 | 3,600 lb |
The yields are the values printed on common bagged mixes, such as the roughly 0.60 cubic feet QUIKRETE lists for an 80-lb bag of its standard concrete mix. Other brands and mixes can differ a little, so read the yield on the bag you actually buy and divide 27 by it.
The formula
For a full yard of 80-lb mix that is 27 ÷ 0.60 = 45 bags. The weight column above is just 45 × 80 lb, which is 3,600 lb of dry mix before water. That is a lot of lifting and mixing, and it is the main reason people switch to a truck for larger jobs.
Bags needed for common slab sizes
Find the slab volume first (length × width × thickness in feet, divided by 27 for yards), then divide the cubic feet by the bag yield. The table below is for a 4-inch slab with no waste allowance, using 80-lb bags.
| Slab size | Cubic yards | 80-lb bags |
|---|---|---|
| 8 × 8 ft | 0.79 | 36 |
| 10 × 10 ft | 1.23 | 56 |
| 12 × 12 ft | 1.78 | 80 |
| 12 × 16 ft | 2.37 | 107 |
| 20 × 20 ft | 4.94 | 223 |
Use the concrete calculator for any other size or for footings, walls, columns and steps. It also returns bag counts for all three bag sizes. If you already have a volume in cubic feet or inches, the cubic yard calculator converts it.
Worked example: a 10 × 10 patio
A patio slab 10 ft by 10 ft and 4 inches thick has 10 × 10 × (4 ÷ 12) = 33.3 cubic feet, which is 1.23 cubic yards. Bags are bought whole, so with no allowance you round 33.3 ÷ 0.60 = 55.6 up to 56 bags.
Now add a 10% waste allowance, which is a common planning figure. The volume becomes about 36.7 cubic feet, or 1.36 cubic yards, and the bag count becomes 62 bags of 80-lb mix. Concrete Network suggests ordering an extra 10 to 15 percent to cover spillage and uneven subgrade, so treat 10% as the low end for a patio poured on a hand-dug base.
Bags or ready-mix?
The break-even depends on your labor and local prices, but the arithmetic is easy to run yourself. Suppose an 80-lb bag costs $6 where you live (check your store, this is only an example). A full yard in bags is 45 × $6 = $270. If a local supplier quotes a yard of ready-mix at, say, $165 plus a delivery or short-load fee, the truck can be cheaper before you count your time. Ready-mix suppliers often set a minimum order, so call two or three and ask for the delivered price on your exact volume.
- Under about 1 cubic yard: bags are usually the practical choice, such as post holes, a small pad or a few footings.
- 1 to 2 yards: compare both. A short-load fee on a truck can make bags competitive.
- Over 2 yards: hand mixing 90 or more bags is slow, and the batches vary. Ready-mix usually wins on speed and consistency.
Common mistakes
- Using one bag count for every brand. Yield changes with bag size and product. Divide 27 by the number on your bag.
- Forgetting the waste allowance. Running out mid-pour risks a cold joint where fresh and partly set concrete meet.
- Mixing up units. Thickness is in inches, length and width in feet. Convert inches to feet before multiplying, or the answer is 12 times off.
- Counting the bag weight as the concrete weight. Mixed concrete weighs about 4,000 pounds per cubic yard according to Concrete Network, because water is added to the dry mix.
- Mixing too many bags by hand. A pour you cannot finish before the surface stiffens will look and perform worse. Split large pours into sections with forms, or bring in help or a truck.
What else to order or consider
A slab needs a compacted base, forms, and often wire mesh or rebar for crack control. The gravel calculator gives tons for the base from the same dimensions. Wear eye protection and a dust mask when pouring dry mix, since cement dust irritates skin and lungs. For anything structural, such as a footing that carries a wall or deck, follow your local building code and ask the building department or an engineer what applies.
Calculators for this guide
Frequently asked questions
How many 80-lb bags of concrete make 1 cubic yard?
It takes 45 bags of 80-lb mix, because a cubic yard is 27 cubic feet and each bag yields about 0.60 cubic feet. Check the yield printed on your bag, since it varies by product.
How many bags of concrete do I need for a 10 x 10 slab?
A 10 by 10 foot slab at 4 inches thick is 1.23 cubic yards, which is 56 bags of 80-lb mix with no waste allowance. With 10% extra, plan on 62 bags.
How many 60-lb or 40-lb bags are in a yard?
A cubic yard takes 60 bags of 60-lb mix (0.45 cubic feet each) or 90 bags of 40-lb mix (0.30 cubic feet each).
Sources and further reading
- Concrete Calculator: how much do I need? (bags and yards) — The Concrete Network
- How Many Square Feet in a Yard of Concrete? — The Concrete Network
- Concrete Mix, Product No. 1101 (data sheet) — QUIKRETE
More guides
Estimates only. Always confirm quantities with your supplier or a qualified contractor before ordering, and add extra for waste and site conditions.