Bag weight and finished concrete volume are different measurements. ConcreteQty converts your project to cubic feet, adds the selected waste allowance, divides by published yield, and rounds up to a whole bag.
| Bag | Published yield | Bags per 1 ft³ |
|---|---|---|
| 40 lb | 0.30 ft³ | 4 |
| 50 lb | 0.375 ft³ | 3 |
| 60 lb | 0.45 ft³ | 3 |
| 80 lb | 0.60 ft³ | 2 |
“Bags per cubic foot” is rounded upward in the table. For purchasing, use the calculator’s exact total instead of multiplying the rounded illustration.
A worked bag-count example
Suppose the measured project contains 10.00 ft³ of concrete. With a 10% allowance, the purchasing volume is 11.00 ft³. Dividing that total by each published yield and rounding up produces 37 forty-pound bags, 30 fifty-pound bags, 25 sixty-pound bags, or 19 eighty-pound bags. The rounding happens after the full project is totaled.
Rounding before the total adds bags
Three separate 2 × 2 ft pads at 4 in need 3 eighty-pound bags each if each pad is rounded alone, which is 9 bags. The same concrete totaled first needs 8 bags. The extra 1 bag is only the early rounding. The bag calculator rounds after the job total.
Check the product you are buying
The cited values come from QUIKRETE Concrete Mix No. 1101. Other mixes and brands can publish different yields, so the label on the actual product takes priority. If a label states a different finished yield, use that yield rather than assuming every bag of the same weight is interchangeable.
Plan more than the purchase count
Bag count is also a handling plan. Check whether the bags can be stored dry, moved safely, mixed within the available working time, and supplied with the required water. A lower bag price does not by itself account for mixing equipment, labor, cleanup, or placement pace.
Run these numbers in the bag calculator. The cited sources are the yields and ordering references behind the count.