Concrete Bag Calculator
Updated Formulas shown
Pre-mixed bags are easiest for small pours: pads, steps, post footings and repairs. A 4 × 4 ft pad at 4 inches takes 10 bags of 80 lb with 10% waste.
- 80 lb bags
- 100.6 ft³ each
- 80 lb bags
- 10
- 60 lb bags
- 14
- Cubic feet
- 5.87 ft³
- Cubic meters
- 0.17 m³
- Weight (wet)
- 880 lb
Includes your waste allowance. Bag yields: 40 lb = 0.30 ft³, 60 lb = 0.45 ft³, 80 lb = 0.60 ft³.
The formula
Bag yields used: 80 lb = 0.60 ft³, 60 lb = 0.45 ft³, 50 lb = 0.375 ft³, 40 lb = 0.30 ft³ (Quikrete and Sakrete published yields). Bags = volume in ft³ ÷ yield, rounded up.
Quick reference
| Slab size | Cubic yards | Cubic feet | 80 lb bags | 60 lb bags | 40 lb bags |
|---|---|---|---|---|---|
| 4 × 4 ft | 0.2 | 5.3 | 9 | 12 | 18 |
| 8 × 8 ft | 0.79 | 21.3 | 36 | 48 | 72 |
| 10 × 10 ft | 1.23 | 33.3 | 56 | 75 | 112 |
| 10 × 12 ft | 1.48 | 40 | 67 | 89 | 134 |
| 10 × 20 ft | 2.47 | 66.7 | 112 | 149 | 223 |
| 12 × 12 ft | 1.78 | 48 | 80 | 107 | 160 |
| 12 × 16 ft | 2.37 | 64 | 107 | 143 | 214 |
| 12 × 20 ft | 2.96 | 80 | 134 | 178 | 267 |
| 16 × 16 ft | 3.16 | 85.3 | 143 | 190 | 285 |
| 20 × 20 ft | 4.94 | 133.3 | 223 | 297 | 445 |
| 20 × 24 ft | 5.93 | 160 | 267 | 356 | 534 |
| 24 × 24 ft | 7.11 | 192 | 320 | 427 | 640 |
| 30 × 30 ft | 11.11 | 300 | 500 | 667 | 1000 |
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Frequently asked questions
How many 80 lb bags of concrete make a yard?
45 bags. A cubic yard is 27 ft³ and each 80 lb bag yields 0.6 ft³.
How many 60 lb bags make a yard?
60 bags (27 ÷ 0.45).
Is it cheaper to buy bags or ready-mix?
Bags win below about 1 cubic yard. Above that, ready-mix is usually cheaper and much faster, even with a short-load fee.
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Estimates only. Check quantities with your supplier or contractor before ordering.