Bags per cubic yard
Bagged concrete is sold by weight, but what matters is the volume it makes once mixed. Manufacturers print that yield on the bag in cubic feet. Typical yields for standard concrete mix:
| Bag size | Typical yield | Bags per cubic foot | Bags per cubic yard |
|---|---|---|---|
| 40 lb | about 0.30 cu ft | 3.33 | 90 |
| 60 lb | about 0.45 cu ft | 2.22 | 60 |
| 80 lb | about 0.60 cu ft | 1.67 | 45 |
bags = cubic feet ÷ yield per bag, rounded up
So one 80 lb bag is 0.60 ÷ 27 = 0.022 cubic yards, and one 60 lb bag is 0.45 ÷ 27 = 0.017 cubic yards.
Fast-setting, high-strength, fiber-reinforced and mortar or sand mixes can yield differently. If your bag lists a different yield, divide your cubic feet by that number instead.
Worked example
A small landing pad 6 ft × 4 ft, 4 in thick:
- 4 in = 0.333 ft. 6 × 4 × 0.333 = 8 cubic feet
- Add 10 percent: 8.8 cubic feet
- 80 lb bags: 8.8 ÷ 0.60 = 14.7, so 15 bags
- 60 lb bags: 8.8 ÷ 0.45 = 19.6, so 20 bags
That is 1,200 lb of mix either way, which is worth knowing before it goes in the car.
Bags for common small jobs
No waste added. Hole volumes subtract the post.
| Job | Concrete needed | 80 lb bags | 60 lb bags |
|---|---|---|---|
| Fence post, 4 × 4 in a 10 in hole 24 in deep | 0.92 cu ft | 2 | 3 |
| Fence post, 4 × 4 in a 10 in hole 36 in deep | 1.38 cu ft | 3 | 4 |
| Deck post, 6 × 6 in a 12 in hole 36 in deep | 1.73 cu ft | 3 | 4 |
| Deck post, 6 × 6 in a 12 in hole 48 in deep | 2.30 cu ft | 4 | 6 |
| Pad 3 × 3 ft, 4 in thick | 3 cu ft | 5 | 7 |
| Pad 4 × 4 ft, 4 in thick | 5.33 cu ft | 9 | 12 |
| Sidewalk section 4 × 10 ft, 4 in thick | 13.3 cu ft | 23 | 30 |
| Pier tube 8 in across, 4 ft deep | 1.40 cu ft | 3 | 4 |
| Pier tube 12 in across, 4 ft deep | 3.14 cu ft | 6 | 7 |
A 4 × 4 post measures 3.5 in square and a 6 × 6 measures 5.5 in square, which is what these figures subtract. For more hole and tube sizes, see the footing and post hole calculator.
Bag coverage by thickness
How much area one bag fills:
| Thickness | 80 lb bag covers | 60 lb bag covers |
|---|---|---|
| 2 in | 3.6 sq ft | 2.7 sq ft |
| 3 in | 2.4 sq ft | 1.8 sq ft |
| 4 in | 1.8 sq ft | 1.35 sq ft |
| 6 in | 1.2 sq ft | 0.9 sq ft |
When bags stop making sense
The bag count climbs fast. One cubic yard is 45 bags of 80 lb: 3,600 lb to haul, lift and mix, and the batches need to go in close enough together that they bond. For a 10 × 10 ft patio that is 56 bags before any extra. Many people switch to ready-mix somewhere around a cubic yard, and plenty of plants offer small loads. Price both ways: bag count × bag price against a delivered quote. Concrete cost per yard walks through the comparison.
Tips for mixing bagged concrete
- Use the water amount on the bag. Extra water makes it easier to place but weaker once cured.
- Mix full bags. Splitting bags changes the ratio of cement to stone and sand.
- Keep spare bags. Buy one or two over the count; most stores take back unopened bags, but check their policy.
- Store bags dry and off the ground. Damp bags start to harden in the sack.
Yields here are typical for standard concrete mix. Use the yield printed on the bag you buy, and round up to whole bags.
Questions people ask
- How many bags of concrete are in a yard?
- About 45 bags of 80 lb (0.60 cu ft each), 60 bags of 60 lb (0.45 cu ft each) or 90 bags of 40 lb (0.30 cu ft each). A cubic yard is 27 cubic feet, and 27 ÷ bag yield = bags.
- How many yards is one 80 lb bag of concrete?
- About 0.022 cubic yards. An 80 lb bag yields about 0.60 cubic feet, and 0.60 ÷ 27 = 0.022, roughly 1/45 of a cubic yard.
- How many square feet does an 80 lb bag of concrete cover?
- About 1.8 sq ft at 4 inches thick, 2.4 sq ft at 3 inches, and 1.2 sq ft at 6 inches.
- How many bags of concrete do I need for a fence post?
- It depends on the hole. A 10 in hole 2 ft deep around a 4 × 4 post takes about 0.92 cubic feet: 2 bags of 80 lb or 3 bags of 60 lb.
- Is it cheaper to use bags or ready-mix?
- For small jobs bags usually win because ready-mix has minimums and small-load fees. For larger pours, compare 45 × your bag price against a delivered price per yard from a local plant.