Concrete bag chart
| Slab | Thick | Cubic yards (+10%) | 80 lb bags | 60 lb bags |
|---|---|---|---|---|
| 4 × 4 ft | 4 in | 0.22 | 10 | 14 |
| 4 × 4 ft | 5 in | 0.27 | 13 | 17 |
| 4 × 4 ft | 6 in | 0.33 | 15 | 20 |
| 8 × 8 ft | 4 in | 0.87 | 40 | 53 |
| 8 × 8 ft | 5 in | 1.09 | 49 | 66 |
| 8 × 8 ft | 6 in | 1.30 | 59 | 79 |
| 10 × 10 ft | 4 in | 1.36 | 62 | 82 |
| 10 × 10 ft | 5 in | 1.70 | 77 | 102 |
| 10 × 10 ft | 6 in | 2.04 | 92 | 123 |
| 10 × 12 ft | 4 in | 1.63 | 74 | 98 |
| 10 × 12 ft | 5 in | 2.04 | 92 | 123 |
| 10 × 12 ft | 6 in | 2.44 | 110 | 147 |
| 12 × 12 ft | 4 in | 1.96 | 88 | 118 |
| 12 × 12 ft | 5 in | 2.44 | 110 | 147 |
| 12 × 12 ft | 6 in | 2.93 | 132 | 176 |
| 12 × 20 ft | 4 in | 3.26 | 147 | 196 |
| 12 × 20 ft | 5 in | 4.07 | 184 | 245 |
| 12 × 20 ft | 6 in | 4.89 | 220 | 294 |
| 20 × 20 ft | 4 in | 5.43 | 245 | 326 |
| 20 × 20 ft | 5 in | 6.79 | 306 | 408 |
| 20 × 20 ft | 6 in | 8.15 | 367 | 489 |
| 24 × 24 ft | 4 in | 7.82 | 352 | 470 |
| 24 × 24 ft | 5 in | 9.78 | 440 | 587 |
| 24 × 24 ft | 6 in | 11.73 | 528 | 704 |
The formula
Cubic feet = length (ft) × width (ft) × thickness (in) ÷ 12
Add 10% for spillage and uneven ground
Bags = cubic feet ÷ bag yield (80 lb = 0.60 ft³, 60 lb = 0.45 ft³, 40 lb = 0.30 ft³), rounded up
Bag yields are the manufacturers’ published figures for standard concrete mix. High-strength and fast-setting mixes yield slightly less per bag; check the bag.
Past roughly a cubic yard, ready-mix delivery usually beats bags on price and labor. See bags vs ready-mix, or use the concrete calculator with your own size.
Typical 2026 US prices used in the tables: 80 lb concrete $6.50, ready-mix $170/yd³ plus a $150 short-load fee under 4 yd³; gravel $5.50 per 0.5 ft³ bag or $45/ton + $100 delivery; mulch $4 per 2 ft³ bag or $40/yd³ + $75 delivery; topsoil $3.25 per 0.75 ft³ bag or $35/yd³ + $75 delivery. Change any of them in the calculators.