Buy whole bags by printed yield
Select the bag size, round up to a whole bag, and replace the nominal yield with the package yield when it differs.
Continue planning
How the calculation works
We use 150 lb/ft³ normal-weight planning value.
Formula: required cubic feet ÷ nominal yield per bag, rounded up
Worked example
A 10 × 10 ft slab at 4 in depth is about 75 60-lb bags or 56 80-lb bags before waste.
Measure the placement volume
Enter the finished dimensions for a small slab, post base, or repair and include voids only when they will be filled.
Nominal bag-yield reference
| Bag size | Nominal yield |
|---|---|
| 40 lb | 0.30 ft³ |
| 60 lb | 0.45 ft³ |
| 80 lb | 0.60 ft³ |
Frequently asked questions
Why does the calculator round up?
Concrete mix is sold in whole bags, so any fraction requires another bag.
Are all bags the same yield?
No. Product recipes and water demand vary, so the package yield controls the final purchase.
Sources and assumptions
NRMCA normal-weight concrete guidance and nominal packaged-mix yields.
Last reviewed: August 14, 2026. Read the methodology and sources.