Concrete Bag Calculator
How many bags of concrete do you need? Enter your pour and get the count for 40, 50, 60 and 80 lb bags, with the lowest-cost size marked.
How many bags of concrete do I need?
Work out the volume in cubic feet, divide by the yield of one bag and round up. Yields are from the QUIKRETE Concrete Mix data sheet.
| Bag size | Yield per bag | Covers at 4 in thick | Bags per cubic yard |
|---|---|---|---|
| 80 lb | 0.60 cu ft | 1.8 sq ft | 45 |
| 60 lb | 0.45 cu ft | 1.35 sq ft | 60 |
| 50 lb | 0.375 cu ft | 1.13 sq ft | 72 |
| 40 lb | 0.30 cu ft | 0.9 sq ft | 90 |
Bags for common jobs
Counts are for 80 lb bags at 4 inches thick, rounded up, with no waste added.
| Job | Cubic feet | 80 lb bags | 60 lb bags |
|---|---|---|---|
| 3 × 3 ft pad | 3.0 | 5 | 7 |
| 4 × 4 ft pad | 5.3 | 9 | 12 |
| 4 × 8 ft pad | 10.7 | 18 | 24 |
| 6 × 6 ft pad | 12.0 | 20 | 27 |
| 8 × 8 ft slab | 21.3 | 36 | 48 |
| 10 × 10 ft slab | 33.3 | 56 | 75 |
Which bag size should I buy?
- 80 lb gives the fewest bags to open and is often the lowest cost per cubic foot.
- 60 lb is easier to lift and pour, and useful when you are working alone.
- 50 lb is the usual size for fast-setting mix used on posts.
- 40 lb suits small repairs.
The calculator marks the size with the lowest total once you enter your store prices.
When to stop using bags
A cubic yard is 45 bags of 80 lb. Above that, ready-mix usually saves time and effort. See bags of concrete per yard for the full table, or compare costs with the concrete calculator.
Frequently asked questions
How many bags of concrete do I need?
Divide your volume in cubic feet by the yield of one bag: 0.60 for 80 lb, 0.45 for 60 lb, 0.375 for 50 lb and 0.30 for 40 lb. Round up, then add 5% to 10% for waste.
How much does an 80 lb bag of concrete cover?
One 80 lb bag makes about 0.60 cubic feet. That covers 1.8 square feet at 4 inches thick.
How much does a 60 lb bag of concrete cover?
One 60 lb bag makes about 0.45 cubic feet. That covers 1.35 square feet at 4 inches thick.
How many 80 lb bags do I need for a 10×10 slab?
56 bags for a 4-inch slab, or 62 bags with 10% added for waste.
Is it cheaper to buy bags or order ready-mix?
It depends on your local prices and the size of the job. Enter your bag price and your supplier’s price per yard in the calculator and it shows both totals.