How many bags of concrete do I need?
One cubic yard of concrete takes 45 bags of 80 lb or 60 bags of 60 lb QUIKRETE Concrete Mix. Formulas, a bag chart for common slabs and post holes, and when to order ready-mix.
- QUIKRETE Concrete Mix yields 0.60 cu ft per 80 lb bag and 0.45 cu ft per 60 lb bag (manufacturer data sheet).
- Per cubic yard (27 cu ft): 45 bags of 80 lb or 60 bags of 60 lb.
- A 10 × 10 ft slab, 4 in thick: 33.3 cu ft, about 56 bags of 80 lb, or 62 bags with 10% extra.
The two-step method
- Work out the volume in cubic feet. Slab or footing: length (ft) × width (ft) × thickness (in) ÷ 12. Round hole: 3.1416 × radius (ft)² × depth (ft).
- Divide by the bag yield printed on the bag, then round up. For QUIKRETE Concrete Mix, the data sheet gives 0.60 cu ft per 80 lb bag and 0.45 cu ft per 60 lb bag.
Add 5–10% for waste, uneven ground and spillage. Our concrete calculator does all of this for you.
Bags per cubic yard
A cubic yard is 3 ft × 3 ft × 3 ft = 27 cubic feet.
| Bag size | Yield | Bags per cubic yard |
|---|---|---|
| 80 lb | 0.60 cu ft | 45 |
| 60 lb | 0.45 cu ft | 60 |
Bag chart for common projects
Before any waste allowance, QUIKRETE Concrete Mix yields:
| Project | Volume | 80 lb bags | 60 lb bags |
|---|---|---|---|
| Slab 4 × 4 ft, 4 in thick | 5.3 cu ft | 9 | 12 |
| Slab 10 × 10 ft, 4 in thick | 33.3 cu ft | 56 | 75 |
| Slab 10 × 10 ft, 6 in thick | 50 cu ft | 84 | 112 |
| Post hole 10 in diameter, 2 ft deep (no post) | 1.09 cu ft | 2 | 3 |
| Post hole 12 in diameter, 3 ft deep (no post) | 2.36 cu ft | 4 | 6 |
For a fence post, subtract the post’s volume: a 4 × 4 post (actual 3.5 × 3.5 in) takes up about 0.085 cu ft per foot of depth.
Bags or ready-mix?
Bags are convenient for post holes, small pads and repairs. They get heavy quickly: 56 bags of 80 lb is over two tons to haul and mix by hand. As a rule of thumb, many DIYers switch to ready-mix delivered by truck once a job reaches about a cubic yard, provided the truck can reach the site (or a pump is booked). Some suppliers also offer small-load or trailer deliveries.
Mixing tips
- Follow the water quantity on the bag: extra water makes concrete easier to place but weaker.
- Mix full bags at a time for consistency.
- Have enough helpers and tools ready before you start, because concrete starts to set within the working time stated on the bag.
Safety and structure
These figures estimate quantities only. Slab thickness, reinforcement and mix strength for structural work should follow local building codes and, where needed, a professional’s specification. Wet concrete is caustic: wear gloves, long sleeves and eye protection.