Slab 1
Length: — ft · Width: — ft · Thickness: — in
Premixed bag estimator
Concrete Bag Calculator
See 40, 50, 60, and 80 lb bag counts at the same time, rounded up with waste included.
Project
Formula
Divide the volume with waste by the label yield
Bag count = concrete volume with waste ÷ published yield per bag, rounded up to a whole bag. ConcreteQty uses QUIKRETE Concrete Mix No. 1101 yields: 0.30, 0.375, 0.45, and 0.60 ft³ for 40, 50, 60, and 80 lb bags.
Common mistake
Rounding each small pad before adding them
Three separate 2 × 2 ft, 4 in pads need 3 eighty-pound bags each if you round every pad, or 9 bags in total. Totalling the concrete first needs 8. The extra 1 bag comes only from rounding early.
Worked quantities
Bag counts for small pours
These jobs are the size where bags are still a handling plan. The weight column is the 80 lb count times 80, so you can see the load before comparing it with a ready-mix order.
| Project | 40 lb bags | 60 lb bags | 80 lb bags | 80 lb weight |
|---|---|---|---|---|
| 4 × 4 ft pad, 4 in | 20 | 14 | 10 | 800 lb |
| 2 × 10 ft sidewalk, 4 in | 25 | 17 | 13 | 1,040 lb |
| 3 ft diameter pad, 4 in | 9 | 6 | 5 | 400 lb |
| 5 × 5 ft, 6 in | 46 | 31 | 23 | 1,840 lb |
| 6 × 8 ft, 4 in | 59 | 40 | 30 | 2,400 lb |
| 8 × 10 ft, 4 in | 98 | 66 | 49 | 3,920 lb |
Field check
Yield matters more than bag weight
Two products with the same bag weight can publish different finished yields. Compare the cubic-foot or liter yield on the actual product label before substituting it for the cited mix.
Field check
Round only after totaling the job
Calculate the full volume first, add the chosen allowance, divide by the product yield, and then round up. Rounding every small section separately can add unnecessary bags.
Field check
Plan the handling load
The result shows several bag sizes at once so you can compare bag count as well as total weight. Storage, lifting, mixing capacity, water access, and working time can matter more than the price difference.
Questions
What the bag calculator answers
Are bag counts rounded up?
Always. A partial bag becomes one whole bag.
Can I add bag prices?
Yes. Open assumptions and costs to enter the price for each bag size.
Do all brands have the same yield?
No. Check the product label and adjust planning when the product differs from the cited yield.
Next step
Check the yield, then compare the handling load
Bag yields follow the cited manufacturer data. See sources and review dates.