Enter the size of the slab or the post holes to see how many bags of concrete mix to buy, and how many pallets.
How many bags of concrete do I need?
Each bag makes a fixed volume of concrete once mixed. Divide the volume you need by the bag's yield and round up.
Bags = volume (cu ft) × (1 + extra %) ÷ yield per bag, rounded up
| Bag | Yield | Bags per cubic yard | Bags per pallet (QUIKRETE) |
|---|
| 80 lb | 0.60 cu ft | 45 | 42 |
| 60 lb | 0.45 cu ft | 60 | 56 |
| 40 lb | 0.30 cu ft | 90 | 80 |
Worked examples
- A 10 × 10 ft pad, 4 in thick: 33.33 cu ft. With 10% extra, 36.67 ÷ 0.6 = 61.1, so 62 bags of 80 lb, or one pallet plus 20 bags.
- Three fence posts in 8 in holes, 24 in deep: each hole is π × (4 in)² × 24 in = 0.70 cu ft. Three holes with 10% extra is 2.30 cu ft, so 4 bags of 80 lb.
Limitations
- Posts take up room: the post itself displaces some concrete, so the hole count here errs on the generous side.
- Yields vary slightly by brand. Check the yield printed on the bag.
- Big jobs: above about a cubic yard (45 bags of 80 lb), ready-mix delivery is usually cheaper. See the concrete cost calculator.
Sources
Learn: Cement vs concrete
How we checked this
Before every update, this calculator is run in a real browser with these known answers, and it must match all of them:
- 10 × 10 ft × 4 in, 10% extra: 62 bags of 80 lb ✓
- Same: 1 pallet + 20 bags ✓
- Same in 60 lb bags: 82 bags ✓
- Three 8 in holes 24 in deep, 10% extra: 4 bags of 80 lb ✓
- Edge: 0.6 cu ft, no extra, is exactly 1 bag ✓
Last checked October 26, 2026. Spotted something wrong? The math is done in your browser with the formula shown on this page, so you can check any result by hand.
Questions people ask
How many 80 lb bags of concrete are in a yard?
45, because each 80 lb bag yields about 0.6 cubic feet and a cubic yard is 27 cubic feet.
How many 60 lb bags of concrete make a yard?
60, at about 0.45 cubic feet per bag.
How many bags of concrete are on a pallet?
For QUIKRETE Concrete Mix: 42 bags of 80 lb, 56 bags of 60 lb or 80 bags of 40 lb.
How much does an 80 lb bag of concrete cover?
About 0.6 cubic feet: 1.8 square feet at 4 inches thick, or 2.4 square feet at 3 inches.
How many bags of concrete for a fence post?
A typical 8-inch hole 2 feet deep takes about 0.7 cubic feet, a little more than one 80 lb bag.