Bags per cubic yard
A cubic yard is 27 cubic feet, so the number of bags is 27 divided by the volume one bag makes. Quikrete publishes these yields for its concrete mix. Other brands are close but not identical, so check the bag.
| Bag size | Yield per bag | Bags per cubic yard | With 10% extra |
|---|---|---|---|
| 40 lb | 0.30 cu ft | 90 | 99 |
| 50 lb | 0.375 cu ft | 72 | 79 |
| 60 lb | 0.45 cu ft | 60 | 66 |
| 80 lb | 0.60 cu ft | 45 | 50 |
Bags for common slabs, 4 inches thick
Counts are rounded up to whole bags and have no waste factor. Add 5 to 10% on a real job.
| Slab | Cubic feet | 80 lb bags | 60 lb bags | 40 lb bags |
|---|---|---|---|---|
| 4 × 4 ft | 5.3 | 9 | 12 | 18 |
| 5 × 5 ft | 8.3 | 14 | 19 | 28 |
| 8 × 8 ft | 21.3 | 36 | 48 | 72 |
| 10 × 10 ft | 33.3 | 56 | 75 | 112 |
| 10 × 12 ft | 40.0 | 67 | 89 | 134 |
| 12 × 12 ft | 48.0 | 80 | 107 | 160 |
| 12 × 20 ft | 80.0 | 134 | 178 | 267 |
When bags stop making sense
A 10 × 10 ft slab at 4 inches needs 56 bags of 80 lb mix, about 4,500 lb of bagged material to mix and place. Past about 1 cubic yard, ready-mix delivery is usually easier, and the concrete cost calculator shows what that slab costs. For posts, the post hole calculator gives bags per hole.
Count the bags for your own size with the concrete calculator.
Bags for real projects
The table counts 80 lb bags at 0.60 cubic feet each, rounded up.
| Project | Size | Concrete | 80 lb bags |
|---|---|---|---|
| Small pad for an AC unit | 3 × 3 ft, 4 in | 3.0 cu ft | 5 |
| Shed base | 8 × 10 ft, 4 in | 26.7 cu ft | 45 |
| Patio | 12 × 12 ft, 4 in | 48.0 cu ft | 80 |
| Walkway | 3 × 20 ft, 4 in | 20.0 cu ft | 34 |
| Garage slab | 20 × 20 ft, 4 in | 133.3 cu ft | 223 |
Mixing and handling
- A truck becomes sensible well before you finish the 40th bag, because mixing bags by hand is slow and uneven.
- Buy the number from the table plus a few spare bags, since a half-filled form is hard to fix.
- Store bags dry and off the ground, and do not use a bag that has set into lumps.
- For fence posts, use the post hole concrete calculator.
Frequently asked questions
How many 80 lb bags of concrete are in a yard?
45 bags. Each 80 lb bag yields about 0.60 cubic feet and a yard is 27 cubic feet.
How many 60 lb bags of concrete make a yard?
60 bags, because each yields about 0.45 cubic feet.
How many 40 lb bags of concrete are in a yard?
90 bags of 40 lb mix, at about 0.30 cubic feet each.