How many 80 lb bags of concrete are in a cubic yard?
At 0.022 yd³ per 80 lb bag, you need about 46 bags per cubic yard. Buy extra to account for overpour and spillage — typically 5% more than your calculated amount.
Concrete planning estimate
Concrete Bag Calculator
Calculate how many 40 lb, 60 lb, or 80 lb bags of concrete you need for any project. Enter your slab, footing, or post hole dimensions to get the exact bag count and volume estimate.
What the bag calculator estimates
Enter your project dimensions and the calculator tells you exactly how many bags of each size you need. It rounds up to whole bags, adds a waste factor, and tells you when ready-mix is more practical.
- Bag count for 40 lb, 60 lb, and 80 lb bags.
- Concrete volume in cubic yards or cubic meters.
- Waste factor recommendation.
- Ready-mix threshold — when bags become impractical.
- Bag mixing effort score for large projects.
Concrete bag count by slab size
Pre-calculated for 4 in thickness, 5% waste. All three bag sizes shown.
| Slab size | Ordered yd³ | 40 lb bags | 60 lb bags | 80 lb bags |
|---|---|---|---|---|
| 4 × 4 × 4 in | 0.21 | 19 | 13 | 10 |
| 6 × 6 × 4 in | 0.47 | 43 | 28 | 22 |
| 8 × 8 × 4 in | 0.83 | 76 | 49 | 38 |
| 10 × 10 × 4 in | 1.30 | 118 | 77 | 59 |
| 12 × 12 × 4 in | 1.87 | 170 | 110 | 85 |
Bags vs. ready-mix: when to switch
Bags are convenient for small jobs. Above about 1 yd³, ready-mix saves time and often costs less per yard.
- Under 0.5 yd³: Bags are the clear choice — small, manageable, no minimum order.
- 0.5–1 yd³: Bags still practical; consider renting a mixer for 40+ bags.
- 1–2 yd³: Ready-mix is worth considering — short-load fees may apply.
- Over 2 yd³: Ready-mix is almost always faster, more consistent, and competitive in cost.
- Over 6 yd³: Ready-mix required — bag mixing is impractical.
Common post hole bag counts
Per-hole estimates with 10% waste for fence posts, deck posts, and anchors.
| Hole size | yd³ per hole | 80 lb bags | 50 lb bags |
|---|---|---|---|
| 8 in × 24 in | 0.028 | 2 | 3 |
| 10 in × 24 in | 0.044 | 3 | 4 |
| 10 in × 36 in | 0.067 | 4 | 5 |
| 12 in × 36 in | 0.096 | 5 | 7 |
Concrete bag calculator FAQ
What is the difference between 40 lb, 60 lb, and 80 lb concrete bags?
All three are typically the same concrete mix in different bag sizes. 80 lb bags are most common and the best value. 60 lb bags are easier to carry. 40 lb bags are for very small jobs or tight access.
When should I switch from bags to ready-mix?
Ready-mix becomes more practical above about 1 cubic yard (46 bags of 80 lb). For a 10 × 10 slab or larger, the time savings and consistent quality of ready-mix usually outweigh the convenience of bags.
How do I mix bagged concrete?
For small jobs, a mixing tub or wheelbarrow works. Above 10–15 bags, a rented electric mixer significantly reduces labor and improves consistency. Always follow the water-to-concrete ratio on the bag.
How long does bagged concrete take to set?
Standard concrete bags set in 24–48 hours and reach full strength in 28 days. Fast-setting concrete (Quikrete Fast-Setting) can reach initial set in 20–40 minutes and support light loads in 4 hours.
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By project type
When bags aren't enough
Planning estimates only
Bag yields vary by brand and product. Always check the yield printed on the bag you buy. These estimates are for planning purposes — confirm with your supplier before purchasing for structural or load-bearing applications.